Amplifier

Abstract: An amplifier which is operated on a low power source voltage and which has a reference voltage of 1.25V or less which temperature characteristic is controllable.

Description: BACKGROUND OF THE INVENTION Field of the invention The present invention relates to an amplifier which is operated on a low power supply voltage and which has a reference voltage which temperature characteristic can be controlled. Description of the prior art This sort of prior art amplifier having a reference voltage independent of temperature has been conventionally arranged as disclosed in JP-A-Ho 2-193410 so that the amplifier comprises a transistor, a resistor and two of first and second current sources, and a positively varying voltage to a temperature obtained by passing a current through the resistor connected at its one end to an input terminal and connected at the other end to the first current source is connected in series with a negatively varying base/emitter voltage of the transistor to the temperature obtained by passing a collector current through the transistor from the second current source to cancel these positively and negatively varying voltages each other and to thereby obtain a reference voltage (about 1.25V) independent of temperature, whereby there is obtained a comparison amplifier which acts as if an amplifier having one input connected to the reference voltage. Since the output terminal voltage of each of the current sources are set to correspond nearly to the diode forward voltage, when such a band gap current source as shown in JP-A-60-191508 is employed, the power source voltage can be lowered down to about 0.9V. Thus, the comparison amplifier can be driven with the power source voltage lower than the reference voltage. The above will be explained in more detail by referring to Fig. 15. Fig. 15 shows an arrangement of a prior art amplifier which has an input terminal 2 to which a voltage from a voltage source 1 is applied and also has an output terminal 3. In the drawing, reference numeral 51 denotes a resistor, numerals 52 and 54 current sources, 53 a transistor. The operation of the prior art will next be explained. In Fig. 15, an addition of a base potential Vb53 of the transistor 53 to a multiplication of a resistive value R51 of the resistor 51 and a current Ics of the current source 52 corresponds to a voltage V1 of the voltage source 1 which is expressed by the following equation (1). V1 = Vb53 + R51 x Ics When the voltage V1 of the voltage source 1 is small, the base voltage Vb53 of transistor 53 becomes also small and the collector current Ic53 of transistor 53 becomes smaller than a current I54 of the current source 54. Thus this causes a tendency of a current to be discharged from the output terminal 3, so that the output voltage V3 becomes high. On the other hand, when the voltage V1 is large, the base voltage Vb53 of transistor 53 becomes also large and the collector current Ic53 of transistor 53 becomes larger than the current I54 of the current source 54. This causes a tendency of a current to be absorbed into the output terminal 3, so that the voltage V3 becomes low. This operation is equivalent to the operation of the amplifier when an inverted input is connected to the input terminal 2, the reference voltage is connected to a non-inverted input, and an output is connected to the output terminal 3. The magnitude of the reference voltage can be found in the following manner. That is, when the voltage V1 of the input terminal 2 becomes equal to the reference voltage, no current flows into and out of the output terminal 3. When such a voltage V1 condition is found, the value of the reference voltage can be known. First, since no current flows into and out of the output terminal 3, the following equation (2) is satisfied. Ic53 = I54 where, Ic53 denotes the collector current of the transistor 53 and I54 denotes the current of the current source 54. At this time, the base potential Vb53 of the transistor 53 is expressed as follows. Vb53 = k x T/q x ln(I54/Is) where, k: Boltzmann factor T: Absolute temperature q: Electric charge for electron Is: The backward saturation current of the transistor Meanwhile, the current source 52 is such a band gap current source as shown in JP-A-60-191508 and the current value Ics of the current source is determined by the following equation (4). Ics = (k x T/q) x In(N)/Rcs where, N denotes a constant and Rcs denotes a current setting resistance. Accordingly, the voltage V1 of the input terminal 2 under such a condition is expressed by the following equation (5) with use of the equations (1), (2) and (4) and the value V1' becomes the reference voltage of the prior art amplifier. V1' = Vb53 + (k x T/q) x ln(N) x R51/Rcs The first term in the equation (5) indicates the diode forward voltage and it is well known that the value of the diode forward voltage is about 650mV and varies with temperature at a rate of -2mV/deg. Hence, when a change to temperature in the second term of the equation (5) is set to have such a value that is opposite in polarity to and is equal in magnitude to the first term, voltage changes to temperature in the first and second terms can be canceled each other. Thus, the reference voltage V1' can be eventually independent of temperature. First, when a voltage change to temperature is found by differentiating the second term with respect to absolute temperature T and the differentiated voltage change is set to be equal to +2mBV, the following equation (6) is obtained. d[equation (5), second term]/dT = (k/q) x ln(N) x R51/Rcs = +2mV Substituting the equation (6) into the second term of the equation (5) and setting T = 300° K results in an equation (7) which follows. [equation (5), second term] = d[equation (5), second term]/dT x T = +2mV x 300° K = 600mV Hence, when the respective constants are set so that {(k x T/q) x ln(N) x R51/Rcs} or (R51 Ics) is 600mV, the reference voltage V1' becomes about 1.25V according to the equation (5) and thus can be eventually set to be independent of temperature. Further, the base potential of the transistor 53 as the terminal voltage of the current source 52 corresponds to the diode forward voltage and the terminal voltage of the current source 5 is determined by a load connected to the output terminal 3. However, when the base of such a common-emitter transistor as the transistor 53 is connected to the output terminal 3, the base potential becomes the diode forward voltage. Thus, when the current sources are realized with such an arrangement as shown in JP-A-60-191508, the power source voltage can be lowered down to about 0.9V. Accordingly, the amplifier can be driven with a power source voltage lower than the reference voltage. In this way, in the prior art amplifier, the reference voltage (about 1.25V) independent of temperature can be obtained and the power source voltage of the amplifier can be lowered to about 0.9V. However, the prior art amplifier has had a first problem that the amplifier requires two current sources, which results in that the necessary circuit area becomes large. A second problem in the prior art amplifier has been that the reference voltage is fixed at about 1.25V so that, when it is desired to set a large reference voltage, this is realized by providing a resistor voltage division means to the input terminal of the amplifier; whereas, when it is desired to set a small reference voltage, this is difficult because the value of the second term of the equation (5) must be made small while undesirably admitting its temperature dependency, that is, the reference voltage value and the temperature characteristic cannot be controlled independently of each other. DE-B-1911934 describes an arrangement comprising a plurality of transistor forming a switching circuit, a current mirror circuit including a plurality of transistors having a conductivity opposite to that of the switching circuit transistors, and a current supply for the current mirror circuit. The current mirror circuit produces the load current and bias current for the switching circuit. EP-A-0322063 describes a signal processor which makes use of current mirror circuitry for addition operation. US-A-4937515 describes a current mirror circuit which has a feedback transistor for reducing the voltage drop at the input of the circuit to less than a certain value. SUMMARY OF THE INVENTION It is an object of the present invention to provide an amplifier which solves or alleviates these problems. According to the present invention there is provided an amplifier capable of operating with a low input voltage supplied thereto and independently of ambient temperature comprising: current mirror circuit means (12, 13); resistor means (11) connected to said current mirror circuit means and to an input of said amplifier; and current generating means (14) connected to said current mirror circuit means and to an output of said amplifier, characterized in that, in operation, a voltage drop across said resistor means is superimposed upon an input potential of said current mirror circuit means to produce a reference voltage at the input of said amplifier. A first embodiment of the invention, has a resistor which is connected to an input of a current mirror circuit and a current generating means is connected to an output of the current mirror circuit. In a second embodiment of the invention, current generating means and resistor voltage-division means are connected to the input and output of the current mirror circuit respectively, and another current generating means is connected to an output of each of the resistor voltage-division means. In a third embodiment of the invention, current generating means and resistor voltage-division means are connected to an input of a current mirror circuit, and another current generating means is connected to an output of the resistor voltage-division means so that a current comparing means compares output currents of two voltage/current converting means. In a fourth embodiment of the fourth invention, a current generating means is connected to each of the input and output of a current mirror circuit, a resistor is connected to the input of the current mirror circuit, a resistor voltage-division means is connected to the output of the current mirror circuit, and another current generating means is connected to an output of the resistor voltage-division means. In a fifth embodiment of the invention, a current generating means is connected to each of the input and output of a current mirror circuit, a resistor is connected to the output of the current mirror circuit, a resistor voltage-division means is connected to the input of the current mirror circuit, and another current generating means is connected to an output of the resistor voltage-division means. In a sixth embodiment of the invention a current generating means and a resistor voltage-division means respectively to the input and output of a current mirror circuit. In a seventh embodiment of the invention, a current generating means and a resistor voltage-division means are connected to an input of a current mirror circuit so that a current comparing means compares output currents of two voltage/current converting means. In an eighth embodiment of the invention, a current generating means is connected to each of the input and output of a current mirror circuit, a resistor is connected to the input of the current mirror circuit, and a resistor voltage-division means is connected to the output of the current mirror circuit. In a ninth embodiment of the invention, a current generating means is connected to each of the input and output of a current mirror circuit, a resistor is connected to the output of the current mirror circuit, and a resistor voltage-division means is connected to the input of the current mirror circuit. In a tenth embodiment of the invention a resistor voltage-division means is connected to each of the input and output of a current mirror circuit, and current generating means is connected to outputs of the respective resistor voltage-division means. In an eleventh embodiment of the invention, a resistor voltage-division means is connected to an input of a current mirror circuit, and a current generating means is connected to the resistor voltage-division means so that a current comparing means compares output currents of two voltage/current converting means. In a twelfth embodiment of the invention, a resistor is connected to an input of a current mirror circuit, a resistor voltage-division means is connected to an output of the current mirror circuit, and a current generating means is connected to an output of the resistor voltage-division means. In a thirteenth embodiment of the invention a resistor is connected to an output of a current mirror circuit, and a resistor voltage-division means is connected to an input of the current mirror circuit, and a current generating means is connected to an output of the resistor voltage-division means. Therefore, in accordance with the first embodiment of the invention, the reference voltage is obtained by adding a negatively varying voltage (to temperature) of the diode forward voltage of the diode-connected transistor at the input of the current mirror circuit to a positively varying voltage (to temperature) of input current times resistance obtained when the output current of the current mirror circuit is equal to the current of the current generating means, so that the temperature characteristic can be advantageously controlled by changing a ratio between these varying voltages. Further, when the output terminal voltage is set to be below 0.7V and such a low-voltage operated type current generating means as shown in JP-A-60-191508 is employed, the power source voltage of the amplifier can be advantageously lowered to about 0.9V. In accordance with the second embodiment of the invention, the resistor voltage-division means and the two current generating means are provided to each of the input and output of the current mirror circuit so that the amplifier comprise the similar circuits which are the same and similar in the voltages and currents of the corresponding elements. When the first and second input terminal voltages are equal to each other, the both circuits are similar so that the output current of the current mirror circuit is equal to the current of the current generating means provided at its junction point so that the input voltage becomes equal to the reference voltage. When the voltage at the output of the resistor voltage-division means at the input of the current mirror circuit connected to the input terminal is changed, the similar condition of the both circuits is destroyed and the balance between the output current of the current mirror circuit and the current of the current generating means at its junction point is destroyed, so that a current or voltage corresponding to a variation in the current or voltage at the input terminal appears at the output terminal. The reference voltage is equivalently obtained by adding a negatively varying forward voltage (to temperature) of the diode-connected transistor provided at the input of the current mirror circuit through which the current of the current generating means flows, to a positively varying voltage (to temperature) obtained through the current generating means and resistor voltage-division means; and further by multiplying the obtained addition by the voltage division ratio of the resistor voltage-division means. Thus, by changing the ratio of these varying voltages, the temperature characteristic can be advantageously controlled. When the reference voltage and the output terminal voltage are set to be 0.7V or less and such a low-voltage operated type current generating means as shown in JP-A-60-191508 is employed, the power source voltage can be advantageously lowered to about 0.9V. In accordance with the third embodiment of the invention, the resistor voltage-division means and the two current generating means are connected to the input of the current mirror circuit, and the voltage/current converting means forms the similar circuits which are the same and similar in the voltage and current of the corresponding elements. When the first and second input terminal voltages are equal to each other, the both circuits are put in their similar condition, in which the output currents of the current mirror circuits become equal and the output of the current comparing means becomes zero. When the voltage at the output of the resistor voltage-division means provided at the input of the current mirror circuit connected to one input terminal is changed and the similar condition between the both circuits is destroyed, a current or voltage corresponding to a variation in the current or voltage at the input terminal appears at the output terminal. The reference voltage is equivalently obtained by adding a negatively varying forward voltage (to temperature) of the diode-connected transistor provided at the input of the current mirror circuit through which the current of the current generating means flows, to a positively varying voltage (to temperature) obtained through the current generating means and resistor voltage-division means; and further by multiplying the obtained addition by the voltage division ratio of the resistor voltage-division means. Thus, the reference voltage can be set to be less than 1.25V. Further, by changing the ratio of these varying voltages, the temperature characteristic can be advantageously controlled. When the reference voltage and the output terminal voltage are set to be 0.7V or less, such a low-voltage operated type current generating means as shown in JP-A-60-191508 is employed, and the current comparing means is formed to have a current mirror structure; the power source voltage can be advantageously lowered to about 0.9V. The fourth embodiment of the invention corresponds in arrangement to the second embodiment of the invention but with one current generating means provided at the input side of the current mirror circuit and the resistor provided at the ground side of the resistor voltage-division means being removed. When the input voltage is equal to the reference voltage, the fourth invention comprise the similar circuits which are the same and similar in the voltage and current of the corresponding elements. When the first and second input terminal voltages are equal to each other, the both circuits are put in their similar condition so that the input voltage is equal to the reference voltage. When the voltage at the output of the resistor voltage-division means provided at the input of the current mirror circuit connected to one input terminal is changed and the similar condition between the both circuits is destroyed, and the balance between the output current of the current mirror circuit and the current of the current generating means at its junction point is destroyed, so that a current or voltage corresponding to a variation in the current or voltage at the input terminal appears at the output terminal. The reference voltage is equivalently obtained by adding a negatively varying forward voltage (to temperature) of the diode-connected transistor provided at the input of the current mirror circuit through which the current of the current generating means flows, to a positively varying voltage (to temperature) obtained through the current generating means and resistor voltage-division means; and further by multiplying the obtained addition by the voltage division ratio of the resistor voltage-division means. Thus, the reference voltage can be set to be less than 1.25V. Further, by changing the ratio of these varying voltages, the temperature characteristic can be advantageously controlled. When the reference voltage and the output terminal voltage are set to be 0.7V or less, such a low-voltage operated type current generating means as shown in JP-A-60-191508 is employed, the power source voltage can be advantageously lowered to about 0.9V. Further, since the number of necessary current generating means is decreased, the fourth embodiment of the invention can be economically arranged advantageously. The fifth embodiment of the invention corresponds in arrangement to the second embodiment of the invention but with one current generating means provided at the output side of the current mirror circuit and the resistor provided at the ground side of the resistor voltage-division means being removed. When the input voltage is equal to the reference voltage, the fourth invention comprise the similar circuits which are the same and similar in the voltage and current of the corresponding elements. When the first and second input terminal voltages are equal to each other, the both circuits are put in their similar condition so that the input voltage is equal to the reference voltage. When the voltage at the output of the resistor voltage-division means provided at the input of the current mirror circuit connected to one input terminal is changed and the similar condition between the both circuits is destroyed, and the balance between the output current of the current mirror circuit and the current of the current generating means at its junction point is destroyed, so that a current or voltage corresponding to a variation in the current or voltage at the input terminal appears at the output terminal. The reference voltage is equivalently obtained by adding a negatively varying forward voltage (to temperature) of the diode-connected transistor provided at the input of the current mirror circuit through which the current of the current generating means flows, to a positively varying voltage (to temperature) obtained through the current generating means and resistor voltage-division means; and further by multiplying the obtained addition by the voltage division ratio of the resistor voltage-division means. Thus, the reference voltage can be set to be 1.25V or less. Further, by changing the ratio of these varying voltages, the temperature characteristic can be advantageously controlled. When the reference voltage and the output terminal voltage are set to be 0.7V or less, such a low-voltage voltage operated type current generating means as shown in JP-A-60-191508 is employed, the power source voltage can be advantageously lowered to about 0.9V. Further, since the number of necessary current generating means is decreased, the fourth embodiment of the invention can be economically arranged advantageously. In accordance with the sixth embodiment of the invention, the resistor voltage-division means and the current generating means are provided to each of the input and output of the current mirror circuit and the sixth embodiment of the invention comprises the similar circuits which are the same and similar in the voltage and current of the corresponding elements. When the first and second input terminal voltages are equal to each other, the both circuits are put in their similar condition, in which the output current of the current mirror circuit becomes equal to the current of the current generating means provided at its junction point, whereby the input voltage becomes equal to the reference voltage. When the output voltage through the resistance voltage division at the input of the current mirror circuit connected to the input terminal is changed and the similar condition between the both circuits is destroyed, the balance between the output current of the current mirror circuit and the current of the current generating means at its junction point is destroyed, a current or voltage corresponding to a variation in the current or voltage at the input terminal appears at the output terminal. The reference voltage corresponds equivalently to a multiplication of the forward voltage of the diode-connected transistor provided at the input of the current mirror circuit obtained through passage of the current of the current generating means by the voltage division ratio of the resistor voltage-division means. Thus a negatively varying reference voltage to temperature can be obtained and further since the number of necessary current generating means is decreased, the sixth embodiment of the invention can be economically arranged advantageously. When the reference voltage and the output terminal voltage are set to be 0.7V or less and such a low-voltage operated type current generating means as shown in JP-A-60-191508 is employed, the power source voltage can be advantageously lowered to about 0.9V. In accordance with the seventh embodiment of the invention, the resistor voltage-division means and the current generating means are connected to the input of the current mirror circuit, and the voltage/current converting means forms the similar circuits which are the same and similar in the voltage and current of the corresponding elements. When the first and second input terminal voltages are equal to each other, the both circuits are put in their similar condition, in which the output currents of the current mirror circuits become equal and the output of the current comparing means becomes zero. When the output voltage of the resistor voltage-division means provided at the input of the current mirror circuit connected to one input terminal is changed and the similar condition between the both circuits is destroyed, a current or voltage corresponding to a variation in the current or voltage at the input terminal appears at the output terminal. The reference voltage is equivalently obtained by multiplying the forward voltage of the diode-connected transistor provided at the input of the current mirror circuit obtained through passage of the current of the current generating means by the voltage division ratio of the resistor voltage-division means. Thus, a negatively varying reference voltage to temperature can be obtained. Further, since the number of necessary current generating means is reduced, the seventh embodiment of the invention can be economically arranged advantageously. When the reference voltage and the output terminal voltage are set to be 0.7V or less, such a low-voltage operated type current generating means as shown in JP-A-60-191508 is employed, and the current comparing means is formed to have a current mirror structure; the power source voltage can be advantageously lowered to about 0.9V. The eighth embodiment of the invention corresponds in arrangement to the sixth embodiment of the invention but with the resistor at the ground side of the resistor voltage-division means provided at the input side of the current mirror circuit and the resistor provided at the ground side of the resistor voltage-division means being removed. When the input voltage is equal to the reference voltage, the fourth embodiment of the invention comprise the similar circuits which are the same and similar in the voltage and current of the corresponding elements. When the first and second input terminal voltages are equal to each other, the both circuits are put in their similar condition so that the input voltage is equal to the reference voltage. When the voltage at the output of the resistor voltage-division means provided at the input of the current mirror circuit connected to one input terminal is changed and the similar condition between the both circuits is destroyed, and the balance between the output current of the current mirror circuit and the current of the current generating means at its junction point is destroyed, so that a current or voltage corresponding to a variation in the current or voltage at the input terminal appears at the output terminal. The reference voltage is equivalently obtained by multiplying the forward voltage obtained through passage of the current of the current generating means through the diode-connected transistor provided at the input of the current mirror circuit by the voltage division ratio of the resistor voltage-division means. Thus, a negatively varying reference voltage to temperature can be obtained. Further, since the number of necessary current generating means is reduced, the eighth embodiment of the invention can be economically arranged advantageously. When the reference voltage and the output terminal voltage are set to be 0.7V or less, such a low-voltage operated type current generating means as shown in JP-A-60-191508 is employed, the power source voltage can be advantageously lowered to about 0.9V. The ninth embodiment of the invention corresponds in arrangement to the sixth embodiment of the invention but with the resistor at the ground side of the resistor voltage-division means provided at the input side of the current mirror circuit and the resistor provided at the ground side of the resistor voltage-division means being removed. When the input voltage is equal to the reference voltage, the fourth invention comprise the similar circuits which are the same and similar in the voltage and current of the corresponding elements. When the first and second input terminal voltages are equal to each other, the both circuits are put in their similar condition so that the input voltage is equal to the reference voltage. When the voltage at the output of the resistor voltage-division means provided at the input of the current mirror circuit connected to one input terminal is changed and the similar condition between the both circuits is destroyed, and the balance between the output current of the current mirror circuit and the current of the current generating means at its junction point is destroyed, so that a current or voltage corresponding to a variation in the current or voltage at the input terminal appears at the output terminal. The reference voltage is equivalently obtained by multiplying the forward voltage obtained through passage of the current of the current generating means through the diode-connected transistor provided at the input of the current mirror circuit by the voltage division ratio of the resistor voltage-division means. Thus, a negatively varying reference voltage to temperature can be obtained. Further, since the number of necessary current generating means is reduced, the eighth embodiment of the invention can be economically arranged advantageously. When the reference voltage and the output terminal voltage are set to be 0.7V or less, such a low-voltage operated type current generating means as shown in JP-A-60-191508 is employed, the power source voltage can be advantageously lowered to about 0.9V. In accordance with the tenth embodiment of the invention, the resistor voltage-division means and the current generating means are provided to each of the input and output of the current mirror circuit. The tenth embodiment of the invention comprises the similar circuits which are the same and similar in the voltage and current of the corresponding elements. When the first and second input terminal voltages are equal to each other, the both circuits are put in their similar condition so that the input voltage is equal to the reference voltage. When the voltage at the output of the resistor voltage-division means provided at the input of the current mirror circuit connected to one input terminal is changed and the similar condition between the both circuits is destroyed, and the balance between the output current of the current mirror circuit and the current of the current generating means at its junction point is destroyed, so that a current or voltage corresponding to a variation in the current or voltage at the input terminal appears at the output terminal. The reference voltage is equivalently obtained by adding a negatively varying forward voltage (to temperature) of the diode-connected transistor provided at the input of the current mirror circuit through which the current of the current generating means flows, to a positively varying voltage (to temperature) obtained through the current generating means and resistor voltage-division means; and further by multiplying the obtained addition by the voltage division ratio of the resistor voltage-division means. Thus, the reference voltage can be set to be 1.25V or less. Further, by changing the ratio of these varying voltages, the temperature characteristic can be advantageously controlled. The reference voltage settable in the tenth invention is limited to more than diode forward voltage, but since the number of necessary current generating means is reduced, the tenth embodiment of the invention can be economically arranged advantageously. When such a low-voltage operated type current generating means as shown in JP-A-60-191508 is employed, the power source voltage can be advantageously lowered to the reference voltage of +0.2V. Further, since the number of necessary current generating means is decreased, the fourth embodiment of the invention, the be economically arranged advantageously. In accordance with the eleventh embodiment of the invention, the resistor voltage-division means and the current generating means are connected to the input of the current mirror circuit, and the voltage/current converting means forms the similar circuits which are the same and similar in the voltage and current of the corresponding elements. When the first and second input terminal voltages are equal to each other, the both circuits are put in their similar condition, in which the output currents of the current mirror circuits become equal and the output of the current comparing means becomes zero. When the voltage at the output of the resistor voltage-division means provided at the input of the current mirror circuit connected to one input terminal is changed and the similar condition between the both circuits is destroyed, a current or voltage corresponding to a variation in the current or voltage at the input terminal appears at the output terminal. The reference voltage is equivalently obtained by adding a negatively varying forward voltage (to temperature) of the diode-connected transistor provided at the input of the current mirror circuit through which the current of the current generating means flows, to a positively varying voltage (to temperature) obtained through the current generating means and resistor voltage-division means; and further by multiplying the obtained addition by the voltage division ratio of the resistor voltage-division means. Thus, the reference voltage can be set to be less than 1.25V. Further, by changing the ratio of these varying voltages, the temperature characteristic can be advantageously controlled. The reference voltage settable in the eleventh embodiment of the invention is limited to more than diode forward voltage, but since the number of necessary current generating means is reduced, the eleventh embodiment of the invention can be economically arranged advantageously. When such a low-voltage operated type current generating means as shown in JP-A-60-191508 is employed and the current comparing means is made to have a current mirror type, the power source voltage can be advantageously lowered to the reference voltage of +0.2V. The twelfth embodiment of the invention corresponds in arrangement to the tenth embodiment of the invention but with current generating means provided at the input side of the current mirror circuit and the resistor provided at the ground side of the resistor voltage-division means being removed. When the input voltage is equal to the reference voltage, the fourth embodiment of the invention comprise the similar circuits which are the same and similar in the voltage and current of the corresponding elements. When the first and second input terminal voltages are equal to each other, the both circuits are put in their similar condition so that the input voltage is equal to the reference voltage. When the voltage at the output of the resistor voltage-division means provided at the input of the current mirror circuit connected to one input terminal is changed and the similar condition between the both circuits is destroyed, and the balance between the output current of the current mirror circuit and the current of the current generating means at its junction point is destroyed, so that a current or voltage corresponding to a variation in the current or voltage at the input terminal appears at the output terminal. The reference voltage is equivalently obtained by adding a negatively varying forward voltage (to temperature) of the diode-connected transistor provided at the input of the current mirror circuit through which the current of the current generating means flows, to a positively varying voltage (to temperature) obtained through the current generating means and resistor voltage-division means; and further by multiplying the obtained addition by the voltage division ratio of the resistor voltage-division means. Thus, the reference voltage can be set to be less than 1.25V. Further, by changing the ratio of these varying voltages, the temperature characteristic can be advantageously controlled. The reference voltage settable in the eleventh embodiment of the invention is limited to more than diode forward voltage, but since the number of necessary current generating means is reduced, the eleventh embodiment of the invention can be economically arranged advantageously. When such a low-voltage operated type current generating means as shown in JP-A-60-191508 is employed and the current comparing means is made to have a current mirror type, the power source voltage can be advantageously lowered to the reference voltage of +0.2V. The thirteenth embodiment of the invention corresponds in arrangement to the tenth embodiment of the invention but with current generating means provided at the output side of the current mirror circuit and the resistor provided at the ground side of the resistor voltage-division means being removed. When the input voltage is equal to the reference voltage, the fourth embodiment of the invention comprise the similar circuits which are the same and similar in the voltage and current of the corresponding elements. When the first and second input terminal voltages are equal to each other, the both circuits are put in their similar condition so that the input voltage is equal to the reference voltage. When the voltage at the output of the resistor voltage-division means provided at the input of the current mirror circuit connected to one input terminal is changed and the similar condition between the both circuits is destroyed, and the balance between the output current of the current mirror circuit and the current of the current generating means at its junction point is destroyed, so that a current or voltage corresponding to a variation in the current or voltage at the input terminal appears at the output terminal. The reference voltage is equivalently obtained by adding a negatively varying forward voltage (to temperature) of the diode-connected transistor provided at the input of the current mirror circuit through which the current of the current generating means flows, to a positively varying voltage (to temperature) obtained through the current generating means and resistor voltage-division means; and further by multiplying the obtained addition by the voltage division ratio of the resistor voltage-division means. Thus, the reference voltage can be set to be less than 1.25V. Further, by changing the ratio of these varying voltages, the temperature characteristic can be advantageously controlled. The reference voltage settable in the eleventh embodiment of the invention is limited to more than diode forward voltage, but since the number of necessary current generating means is reduced, the eleventh embodiment of the invention can be economically arranged advantageously. When such a low-voltage operated type current generating means as shown in JP-A-60-191508 is employed and the current comparing means is made to have a current mirror type, the power source voltage can be advantageously lowered to the reference voltage of +0.2V. The invention will be described now by way of example only, with particular reference to the accompanying drawings. In the drawings: BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1A is an arrangement of an amplifier in accordance with a first embodiment of the invention; Fig. 1B is an arrangement of an amplifier in accordance with a second embodiment of the invention; Fig. 2 is an arrangement of an amplifier in accordance with a third embodiment of the invention; Fig. 3 is an arrangement of an amplifier in accordance with a fourth embodiment of the invention; Fig. 4 is an arrangement of an amplifier in accordance with a fifth embodiment of the invention; Fig. 5 is an arrangement of an amplifier in accordance with a sixth embodiment of the invention; Fig. 6 is an arrangement of an amplifier in accordance with a seventh embodiment of the invention; Fig. 7 is an arrangement of an amplifier in accordance with an eighth embodiment of the invention; Fig. 8 is an arrangement of an amplifier in accordance with a ninth embodiment of the invention; Fig. 9 is an arrangement of an amplifier in accordance with a tenth embodiment of the invention; Fig. 10 is an arrangement of an amplifier in accordance with an eleventh embodiment of the invention; Fig. 11 is an arrangement of an amplifier in accordance with a twelfth embodiment of the invention' Fig. 12A is an arrangement of an amplifier in accordance with a thirteenth embodiment of the invention; Fig. 12B is an arrangement of an amplifier in accordance with a fourteenth embodiment of the invention; Fig. 13 is an arrangement of an amplifier in accordance with a fifteenth embodiment of the invention; Fig. 14A is a part of the arrangement of the amplifier of Fig. 2 showing an input side of a current mirror circuit; Fig. 14B is the part of Fig. 14A but in which a current source 24 and a transistor 25 are expressed in the form of an equivalent circuit; Fig. 14C is the part of Fig. 14A but in which the current source 24, transistor 25, resistors 22 and 23 are expressed in the form of an equivalent circuit; and Fig. 15 is an arrangement of a prior art amplifier. DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to Fig. 1A, there is shown an arrangement of an amplifier in accordance with a first embodiment of the invention, in which a reference voltage is set to be independent of temperature. In Fig. 1A, the amplifier has an input terminal 2 to which a voltage is applied from a voltage source 1 and also has an output terminal 3. Reference numeral 11 denotes a resistor, and numeral 14 denotes a current source. Transistors 12 and 13 form a current mirror circuit. Explanation will next be made as to the operation of the first embodiment. In Fig. 1A, when a current I2 flows from the input terminal 2, a voltage V1 at the input terminal 2 corresponds to an addition of a base potential Vb12 of the transistor 12 and a multiplication of a resistance Rll of the resistor 11 and the current I2 and is expressed by the following equation (8). V1 = Vb12 + R11 x I2 The current I2 is divided into a collector current Ic12 and a base current (Ib12 + Ib13) at a junction point A of the resistor 11 and the base and collector of the transistor 12. Since a current amplification factor hfe of the transistor is very large, the base current (Ib12 + Ib13) is considered negligible. Further, the collector currents Ic12 and Ic 13 are equal to each other because the transistors 12 and 13 form the current mirror circuit. Accordingly, the following equations (9) and (10) are obtained. I2 = Ic12 + (Ib12 + Ib13) ∴I2 ≒ Ic12 = Ic13 When the voltage Vi is small, the input current Ic12 of the current mirror circuit is small and the output current Ic13 of the current mirror circuit is also small. Thus, since the collector current Ic13 of the transistor 13 is smaller than an current value Ics of the current source 14, an output voltage V3 at the output terminal 3 becomes such a high potential that causes the current to be discharged from the output terminal. When the voltage V1 is large, the collector current Ic13 of the transistor 13 is inversely larger than the current value Ics of the current source 14, which results in that the output voltage V3 becomes such a low potential that causes the current to be absorbed into the output terminal. This operation is equivalent to the operation of an amplifier in which an inverted input is applied to the input terminal 2, a reference voltage is connected to a non-inverted input, and the output terminal 3 is connected to an output. The magnitude of this reference voltage can be found in the following manner. That is, when the voltage V1 at the input terminal 2 becomes equal to the reference voltage, the discharging and absorbing operation of the current at the output terminal 3 disappears. Thus, the value of the reference voltage can be known by finding such a V1 condition. First, an equation (11) is obtained from the condition that no discharging and absorbing operation of the flow from and in the output terminal 3 and also from the equation (10). I14 = Ic13 = I12 ≒ I2 Hence, the base potential Vb12 of the transistor 12 can be expressed by an equation (12) which follows. Vb12 = k x T/q x ln(I2/Is) the current source 14 is such a band gap current source as disclosed in JP-A-60-191508 and the current value Ics of the current source 14 is determined by the equation (4). Accordingly, the voltage V1 at the input terminal 2 under such a condition is expressed by the following equation (13) with use of the equations (8) and (11). The value V1' of the equation (13) corresponds to the reference voltage of the amplifier. V1' = Vb12 + (k x T/q) x ln(N) x R11/Rcs It is well known that the first term in the equation (13) indicates the diode forward voltage, the value of the first term is about 650mV and vary with temperature at a rate of -2mV/deg. Thus, when a variation in the second term of the equation (13) to temperature is set to be equal in magnitude to and to be opposite in polarity to the first term, voltage variations in the first and second terms to temperature can be canceled. Therefore, the reference voltage V1' can be eventually made independent of temperature. When the second term is differentiated with respect to absolute temperature T to find a voltage variation to temperature and the voltage variation is set to be +2mV, the following equation (14) is satisfied. d[second term of equation (13)]/dt = (k/q) x ln(N) x R51/Rcs = +2mV Substituting the equation (14) into the second term of the equation (13) and setting T=300° K results in an equation (15) which follows. [equation (13) second term] = d[equation (13) second term]/dT x T = +2mV x 300° K = 600mV Hence, when the respective constants are set so that (k x T/q) x ln(N) x R11/Rcs or R11 x Ics is equal to 600mV, the reference voltage V1' becomes about 1.25V in accordance with the equation (13) and eventually the temperature-independent voltage can be set. A terminal voltage of the current source 14 is determined by a load connected to the output terminal 3. However, when the base of such a common-emitter transistor as the transistor 13 is connected to the output terminal 3, the terminal voltage becomes the diode forward voltage. Therefore, when the current source 14 is realized with such an arrangement as described in JP-A-60-191508, the power supply voltage can be lowered to about 0.9V. Thus, the amplifier can be driven with the power supply voltage lower than the reference voltage. Since it is seen from the equation (13) that the reference voltage is expressed in terms of a ratio between the resistive value R11 and the resistance Rcs for setting of the current of the current source 14 and is independent of the absolute value of the resistive value, the amplifier circuit can be easily arranged. In this way, the first embodiment has an advantage that, since the reference voltage V1' given by the equation (13) can be expressed in the form of an addition of the forward voltage of the diode-connected transistor 12 to the voltage corresponding in magnitude to the resistance 11 multiplied by the temperature-independent coefficients including the absolute temperature T obtained from the current value Ics of the current source 14 and the resistance ratio, when a ratio between these voltages is changed, the temperature characteristic can be controlled and the amplifier can be arranged with the current source reduced by one in the number of current sources necessary in the prior art. Further, since the terminal voltage of the current source 14 is arranged to correspond to the diode forward direction, when such a low-voltage operated type current source as shown in JP-A-60-191508 is employed, the power source voltage can be lowered down to about 0.9V. Further, since the value of the resistor 13 associated with the reference voltage and the value of the current setting resistor Rcs are given in the form of a ratio in the equation (13), the amplifier can be easily and effectively made in the form of a semiconductor integrated circuit independently of the accuracy of the absolute value. Shown in Fig. lB is an arrangement of an amplifier in accordance with a second embodiment of the invention. The second embodiment of Fig. lB corresponds to the first embodiment of Fig. 1A but in which a transistor 15 and a current source 16 are provided between the output terminal 3 and the junction point B between the current source 14 and the collector of the transistor 13. Explanation will next be made as to the operation of the second embodiment. In Fig. 1B, when the voltage V1 is small, the collector current Ic12 of the transistor 12 as the input current of the current mirror circuit is also small and the collector current Ic13 of the transistor 13 as the output current of the current mirror circuit is also small. This causes the collector current Ic13 of the transistor 13 to be smaller than the current value Ics of the current source 14 so that the base current Ib15 of the transistor 15 increases and a collector current Ic15 thereof also increases. Since the collector current Ic15 is larger than the current I16 of the current source 16, a current tends to flow into the output terminal 3, whereby the output voltage V3 at the output terminal 3 becomes a low potential. On the other hand, when the voltage V1 is large, the collector current Ic13 of the transistor 13 is larger than the current value Ics of the current source 14 so that the base current Ib15 of the transistor 15 decreases and the collector current 15 thereof also decreases. This causes the collector current Ic15 to be smaller than the current I16 of the current source 16, whereby a current tends to flow out of the output terminal 3 and the output voltage V3 becomes a high potential. The operation of the second embodiment of Fig. 1B is substantially the same as that of the first embodiment of Fig. lA, except that the output polarity is different from that of the first embodiment. That is, this operation is equivalent to the operation of an amplifier wherein a non-inverted input is applied to the input terminal 2, a reference voltage is connected to an inverted input, and an output is connected to the output terminal 3. Accordingly, the reference voltage can be also found by the same manner as in the first embodiment. First, since no current flows into and out of the output terminal, the following equation (16) is satisfied. I16 = Ic15 In this case, the currents Ics, Ic13 and Ib15 flowing into and out of the junction point B between the current source 14 and the collector and base of the transistor 13 can be expressed as follows. Ics = Ic13 + Ib15 Assume now that the current I16 of the current source 16 is set to be twice the current value Ics of the current source 14. Then the equation (17) is modified with use of the equation (16), as the following equation (18). Ics = Ic13 + 2 x Ics/hfe Where, symbol hfe denotes the current amplification factor of the transistor. Meanwhile, since a relationship among the respective currents with respect to the junction point A is the same as that in the first embodiment (equation 9), the relationship is expressed by the following equation (19) with use of the factors Ics and hfe and the equation (10). I2 = Ic12 + 2 x Ics/hfe ∴I2 = Ics Hence, it will be seen from the equation (20) that the amplifier is not affected by the base current of the transistor. In more detail, it has been considered in the first embodiment that the current amplification factor hfe of the transistor is very large and thus the base currents Ib12 and Ib13 of the transistors 12 and 13 are negligible. However, strictly speaking, this actually involves a slight error. For the purpose of avoiding this, in the second embodiment, the transistor 15 and the current source 16 are newly added to eliminate the influences of the base current, whereby the accuracy of the reference voltage can be improved and the reference voltage can be made substantially independent of fluctuations in the current amplification factor hfe of the manufactured transistors. In this way, the second embodiment can have, in addition to the advantage of the first invention, an additional advantage of being able to eliminate the influences of the base current of the transistor. With respect to the method for eliminating the influences of the base current, another suitable method may be employed so long as a current having the same magnitude as the base current of the transistor drawn from the junction point A is drawn from the junction point B. Fig. 2 shows an amplifier in accordance with a third embodiment of the invention in which a reference voltage is independent of temperature. In Fig. 2, the illustrated amplifier has a first input terminal 2 to which a voltage is applied from a voltage source 1, a second input terminal 4 to which a voltage is similarly applied from a voltage source 5, and an output terminal 3. The amplifier further includes resistors 22, 23, 32 and 33, current sources 21, 24, 31 and 34, and transistors 25 and 35 making up a current mirror circuit. Explanation will next be made as to the operation of the third embodiment. Assume now in Fig. 2 that the voltage sources 1 and 5 are not connected to input terminals 2 and 4. Under such a condition of Fig. 2, the amplifier has its left and right structures which are the same and have the same constants, except that the transistor 25 is diode-connected. In other words, the resistor 22 corresponds to the resistor 32, the resistor 23 corresponds to the resistor 33, the current source 21 corresponds to the current source 31, the current source 24 corresponds to the current source 34, and the transistor 25 corresponds to the transistor 35, respectively. First, explanation will be made by referring to Figs 14A, 14B and 14C as to the left-side structure including the resistors 22 and 23, the current sources 21 and 24 and the diode-connected transistor 25. In Fig. 14A, since the two signal sources are provided, consider the case where the current source 21 is open-circuited to analyze it by the principle of superposition. Fig. 14B corresponds to Fig. 14A but the diode-connected transistor 25 and the current source 24 are expressed by an equivalent circuit 250. A voltage V251 of a voltage source 251 and a resistive value R252 of a resistance 252 are expressed by the following equations (21) and (22), respectively. V251 = Vf25 R252 = (k x T/q)/Ic25 where, Vf25: The forward voltage of the transistor 25 Ic25: The collector current of the transistor 25 Fig. 14C corresponds to Fig. 14B but the equivalent circuit 250 and the resistors 22 and 23 are expressed by an equivalent circuit 220 by the (Ho)-Thevenin theorem. A voltage V221 of a voltage source 221 and a resistive value R222 of a resistance 222 are expressed by the following equations (23) and (24), respectively. V221 = Vf25 x R23/(R22 + R252 + R23) R222 = (R22 + R252) x R23/(R22 + R252 + R23) where, R22: The resistive value of the resistor 22 R23: The resistive value of the resistor 23 Now, consider the current source 21. The current source 21 is also such a band gap current source as shown in JP-A-60-191508 and the current value Ics of the current source 21 is determined according to the equation (4). Since the current value Ics of the current source 21 flows into the voltage source 221 through the resistance 222, the voltage V2 at input terminal 2 is expressed by the following equation (25). V2 = V221 + R222 x Ics ∴ V2 = M x {Vf25 + (k x T/q) x ln(N) x (R22 + R252)/Rcs} where, M = R23/(R22 + R252 + R23) The equation (25) is very similar to the equation (13) in the first embodiment, so that the voltage V2 independent of temperature can be generated in the same manner as in the first embodiment, More specifically, the first term in the braces {} in the equation (25) indicates the forward voltage of the diode-connected transistor, which is about 650mV and which varies with time at a rate of -2mV/deg. Thus, when the (R22 + R252) and the resistive value Rcs for setting the current of the current source are set so that a change of the second term in the braces {} to temperature becomes +2mV/deg., the voltage changes to temperature in the first and second terms can be canceled each other. This voltage change is the same as the equation (15). Eventually, the voltage V2 can be made independent of temperature and the magnitude of the voltage can be freely set by the factor M. For example, when the voltage V2 is set to be 0.5V, the factor M is set to be 0.5V/1.25V and the resistive and current values R22, R23, 124 and Ics of the resistors 22 and 23 and current sources 24 and 21 can be determined in accordance with the equations (4) and (21) to (25). When the resistive value R22 of the resistance R252 is sufficiently small, the voltage V2 is expressed in the form of a ratio between the resistive values R22, R23 and the resistance Rcs for setting the current of the current source 21, which results in that the voltage V2 becomes independent of the absolute value of the resistive values and thus the amplifier can be easily configured. When the circuit constants thus obtained are allocated to the corresponding elements of the right-side structure of Fig. 2, the right and left structures of Fig. 2 can be the similar circuits which are the same in the voltage and current of the corresponding elements with respect to the current mirror circuit of the transistors 25 and 35. In Fig. 2, a current I24 of the current source 24 is divided at the junction point A into a current I22 to be passed through the resistor 22 and into a branch current toward the transistor 25. The branch current is further divided into a collector current Ic25 of the transistor 25 and the base current (Ib25 + Ib35) of the transistors 25 and 35. Since the transistor 25 has a very large current amplification factor hfe, the base current (Ib25 + Ib35) are negligible and thus the following relationships are satisfied. I24 = I22 + Ic25 + (Ib25 + Ib35) ∴Ic25 ≒ I24 - I22 Meanwhile, a current I34 of the current source 34 is divided at the junction point B into a current I32 to be passed through the resistor 32 and a collector current Ic35 of the transistor 35 and the transistors 25 and 35 make up the current mirror circuit. Thus, since the collector currents Ic25 and Ic35 become equal to each other, the following equation (29) is obtained. I34 = I32 + Ic35 ∴Ic35 = I34 - I32 = Ic25 Since the current value I24 is set to be equal to the current value I34, the equation (30) is satisfied in accordance with the equations (27) and (29). I22 ≒ I32 Hence, since the left and right circuits are same with respect to the current and element constants, the voltages are also the same and these circuits perform the similar operation. The above explanation has been made in connection with the case where no load is connected to the the output terminal 3 connected to the junction point B and thus no current flows into and out of the output terminal 3. The circuit of Fig. 2 under such a condition that no current flows into and out of the output terminal 3, is the same as the state of the first embodiment where the voltage V2 at the input terminal 2 is equal to the reference voltage. Therefore, the similar operation will not be changed regardless of whether or not the voltage source 1 having the same magnitude as the voltage V2 obtained by the equation (25) is connected to the input terminal 2 and the voltage source 5 is similarly connected to the input terminal 4. In the case where the voltage source 5 is not connected and the voltage source 1 is connected, when the voltage V1 supplied from the voltage source 1 is smaller than the reference voltage V2, a voltage across the resistor 22 is increased and the current I22 is increased so that the input current Ic25 of the current mirror circuit becomes small and the output current Ic35 of the current mirror circuit becomes also small. This causes a current flowing into the junction point B to be increased so that the potential V3 at the output terminal 3 becomes high. When the voltage V1 is inversely large, the voltage across the resistor 22 is decreased and the current I22 is decreased. Thus, the current value Ic25 as the input current of the current mirror circuit is increased and the current value I32 as the output current of the current mirror circuit is also increased. This causes a current flowing into the junction point B to be decreased so that the current I32 passing through the resistor 32 decreases and the output voltage V3 at the output terminal 3 becomes low. The above operation is equivalent to the operation of the amplifier when an inverted input is applied to the input terminal 2, the reference voltage is connected to the input terminal 4 receiving a non-inverted input, and an output is connected to the output terminal 3. The above operation has been explained in connection with the case where the voltage is applied to the input terminal 4 and the input terminal 2 is not connected. However, even when a voltage is applied to the input terminal 4 and the input terminal 2 is not connected, the similar operation can be achieved but the polarity becomes opposite to the above. In the latter case, its operation becomes equivalent to the operation of the amplifier wherein the non-inverted input is applied to the input terminal 4, the reference voltage is connected to the input terminal 2 receiving the inverted input, and the output is connected to the output terminal 3. In this case, the reference voltage is expressed by the equation (25) and can be set to be below 1.25V independently of temperature. In this way, the third embodiment has an advantage that, since the reference voltage V2 given by the equation (25) can be expressed in the form of an addition of the forward voltage obtained through the diode-connected transistor 25 and current source 24 to the voltage corresponding in magnitude to the resistance voltage-division means of the resistors 22 and 23 multiplied by the temperature-independent coefficients including the absolute temperature T obtained from the current source 21 and the resistance ratio, when a ratio between these voltages is changed, the temperature characteristic the amplifier can be controlled and and its magnitude can be easily set by the coefficient M. Further, when the terminal voltages of the current sources 24 and 34 are the diode forward voltages and voltages at junction points between the resistors 22 and 23 and between the resistors 32 and 33 as the outputs of the resistance voltage-division means are set to be below the diode forward voltage and when such low-voltage operated current sources as shown in JP-A-60-191508 are employed, the power source voltage can be lowered down to about 0.9V. The third embodiment has an additional effect that, since the values of the resistors 22, 23, 32 and 33 associated with the reference voltage have a relationship in the form of a ratio in the equation (25), the amplifier can be easily made even in the form of a semiconductor integrated circuit independently of the accuracy of the absolute value. In addition, it is seen from the equation (25) that the characteristics of the amplifier to temperature can be determined by (R22 + R252)/Rcs independently of R23, which results in that the decision of the reference voltage can advantageously be freely controlled by the factor R23. Fig. 3 shows an amplifier in accordance with a fourth embodiment of the invention. The amplifier of Fig. 3 includes a first voltage/current converting means comprising the right-side similar circuit of the aforementioned second invention but with the transistor 35 removed, a second voltage/current converting means similar to the first one having an input terminal 4, resistors 42 and 43, current sources 41 and 44, and transistors 45 and 55, a current comparing means 9 having transistors 6 and 7 and a voltage source 8, and an output terminal 3. The operation of the fourth embodiment will be explained. The operation of the first voltage/current converting means is substantially the same as that of the left-side similar circuit of Fig. 2 in the third embodiment, because they have substantially the same structure. The operation of the second voltage/ current converting means is also the same as that of the first one. The voltage when no voltages are applied to the input terminals 2 and 4 is expressed by the equation (25) as in the third embodiment. When the corresponding parts in the first and second voltage/ current converting means have equal currents and element constants, their voltages are also equal to each other and thus the first and second voltage/current converting means perform the similar operation. Thus, the collector currents of the transistors 35 and 55 as the outputs of the first and second voltage/current converting means are equal to each other, whereby no current appears at the output terminal 3 of the current/voltage comparing means 9 for comparing the outputs of the first and second voltage/current converting means. That is, the collector current of the transistor 55 applied to the current mirror circuit of the voltage/current comparing means 9 is converted into a current which is compared with the collector current of the transistor 35 has the same magnitude as the first-mentioned collector current but the opposite direction or sense to the first-mentioned collector current, so that a current corresponding to a difference between the first- and second-mentioned collector currents appears at the output terminal 3. The state of the fourth embodiment of Fig. 3 when no current flows in and out of the output terminal 3 is the same as the state of the third embodiment when the voltage V2 at the input terminal 2 is equal to the reference voltage. This holds true when the voltages applied to the input terminals 2 and 4 are equal to each other. Accordingly, even when the fourth embodiment comprises the two voltage/current converting means and current comparing means, the fourth embodiment can have substantially the same effect as the third embodiment. Shown in Fig. 4 is an amplifier in accordance with a fifth embodiment of the invention which has the same arrangement as the third embodiment but with the current source 21 and the resistor 23 in Fig. 2 removed. Explanation will next be made to the operation of the fifth embodiment. The operation of this embodiment is substantially the same as that of the third embodiment. In more detail, in Fig. 2, when the signal source impedance of the voltage source 1 connected to the input terminal 2 is sufficiently small as compared to the resistive value R22 of the resistor 22, the current flowing through the resistor 22 is determined by the voltage V1 of the voltage source 1. Thus, in the operation of the fifth embodiment, as in the operation of the thid embodiment, the output current or voltage corresponding to a potential difference between the voltage V1 and the reference voltage V2 based on the equation (25) appears at the output terminal 3. At this time, the current of the current source 21 flows into the voltage source 1 and the current flowing through the resistor 23 is supplied from the voltage source 1 and has a magnitude corresponding to the value of the voltage V1. Therefore, it will be seen that these elements do not contribute substantially to the operation of the amplifier. Thus, it will be appreciated that the fifth embodiment can have substantially the same effect as the third embodiment even when the current source 21 and the resistor 23 are eliminated. However, in Fig. 2 showing the third embodiment, wnen the voltage source 1 is not connected, the input terminal 2 has the same potential as the reference voltage V2; whereas, in Fig. 4 showing the fifth embodiment, the potential at the input terminal 2 corresponds to the diode forward voltage. This difference appears in the form of such a phenomenon that, when the signal source impedance of the voltage source 1 is large, the voltage at the input terminal 2 is pulled in which direction from the no-load voltage value of the voltage source. However, the input terminal 4 has the same potential as the reference voltage V2. In this way, even the fifth embodiment can also have, in addition to the same advantage as in the third embodiment, an additional advantage that the voltage source 21 and the resistor 23 can be eliminated and thus the amplifier can be made with a simpler arrangement. Fig. 5 shows an arrangement of an amplifier in accordance with a sixth embodiment, which has substantially the same arrangement as the third embodiment of Fig. 2, except that the current source 31 and the resistor 33 in Fig 2 are eliminated and the voltage source 5 is connected to the input terminal 4. Explanation will next be made as to the operation of the sixth embodiment. The operation of the sixth embodiment is substantially the same as that of the third embodiment. In more detail, in Fig. 2 , when the signal source impedance of the voltage source 5 connected to the input terminal 4 is sufficiently small as compared to the resistive value R32 of the resistor 32, the current flowing through the resistor 32 is determined by the voltage V1 of the voltage source 5. Thus, in the operation of the sixth embodiment, as in the operation of the third embodiment, the output current or voltage corresponding to a potential difference between the voltage V1 and the reference voltage V2 based on the equation (25) appears at the output terminal 3. At this time, the current of the current source 31 flows into the voltage source 5 and the current flowing through the resistor 33 is supplied from the voltage source 5 and has a magnitude corresponding to the value of the voltage V5. Therefore, it will be seen that these elements do not contribute substantially to the operation of the amplifier. Thus, it will be appreciated that the sixth embodiment can have substantially the same effect as the third embodiment even when the current source 31 and the resistor 33 are eliminated. However, in Fig. 2, when the voltage source 5 is not connected, the input terminal 4 has the same potential as the reference voltage V2; whereas, in Fig. 5 showing the sixth embodiment, the potential at the input terminal 4 corresponds to the diode forward voltage. This difference appears in the form of such a phenomenon that, when the signal source impedance of the voltage source 5 is large, the voltage at the input terminal 4 is pulled in which direction from the no-load voltage value of the voltage source. However, the input terminal 2 has the same potential as the reference voltage V2. In this way, even the sixth embodiment can also have, in addition to the same advantage as in the third embodiment, an additional advantage that the voltage source 31 and the resistor 33 can be eliminated and thus the amplifier can be made with a simpler arrangement. Fig. 6 shows an arrangement of an amplifier in accordance with a seventh embodiment, which has substantially the same arrangement as the third embodiment of Fig. 2, except that the current sources 21 and t31 in Fig 2 are eliminated and the diode-connected transistor 25 is provided. The arrangement of Fig. 6 has substantially the same left-side and right-side structures having the same constants. That is, in the left- and right-side structures, the resistor 22 corresponds to the resistor 32, the resistor 23 corresponds to the resistor 33, the current source 24 corresponds to the voltage source 34, and the transistor 25 corresponds to the transistor 35, respectively. The operation of the seventh embodiment will then be explained. The operation of the seventh embodiment is substantially the same as that of the third embodiment. When both or either one of the input terminals 2 and 4 is open-circuited and the other input terminal has the same potential as the reference voltage, the left- and right-side circuits perform the similar operation. However, since the current source 21 and the current source 31 are not provided, the reference voltage has a value expressed by the following equation (31) corresponding to the equation (25) but when the resistance Rcs for setting the current of the current source is set to be infinite. V2 = M x Vf25 where, M = R23/(R22 + R252 + R23) In this way, in the seventh embodiment in Fig. 6, since the diode forward voltage of the diode-connected transistor is utilized as the source of the reference voltage, when the reference voltage is set to be about 650mV, the amplifier can have a temperature characteristic which varies at a rate of -2mV/deg. and the reference voltage can be freely set by multiplying it by the coefficient M. This is advantageous from the viewpoint of the arrangement when a reference voltage having a negative change to temperature is necessary or when the temperature characteristic of the reference voltage has no restrictions and it is desired to reduce the number of necessary elements, since the number of current sources can be reduced by 2 when compared to the third embodiment. The seventh embodiment has substantially the same advantages as the third embodiment, except that the temperature characteristic of the reference voltage is negative and cannot be controlled. Since the terminal voltages of the current sources 24 and 34 do not exceed the diode forward voltage, when such a low-voltage operated type current source as shown in JP-A-60-191508 is employed, the power source voltage can be lowered down to about 0.9V. When the resistive value R252 is sufficiently smaller than the resistive value R22, the voltage V2 can be expressed in the form of a ratio between the resitive values R22 and R23 independent of the absolute value of the resistive values and the circuit formation of the amplifier can be facilitated. Fig. 7 is an arrangement of an amplifier in accordance with an eighth embodiment of the invention, which comprises a first voltage/current converting means corresponding to the right-side similar circuit in Fig. 6 of the seventh embodiment but with transistor 35 removed; a second voltage/current converting means similar to the first one including an input terminal 4, resistors 42 and 43, a current source 44 and transistors 45 and 55; and a voltage/current comparing means 9 including transistors 6 and 7 and a voltage source 8. The amplifier of Fig. 7 also includes an output terminal 3. Explanation will next be made as to the operation of the eighth embodiment. The operation of the first voltage/current converting means in the eighth embodiment is the same as that of the left-side similar circuit having the same structure in Fig. 6 of the seventh embodiment. The operation of the second voltage/current converting means is also the same as that of the above left-side similar circuit. The voltage V2 when no voltages are applied to the input terminals 2 and 4 is expressed by the equation (31) as in the seventh embodiment. Assuming that the first and second voltage/current converting means have the same element constants and the same currents in their corresponding parts, the first and second voltage/current converting means also has the same voltages in their corresponding parts. This means that the first and second voltage/ current converting means perform the similar operation. The collector currents of the transistors 35 and 55 as the outputs of the first and second voltage/current converting means become the same, which results in that no current flows at the output terminal 3 of the current/voltage comparing means 9 for comparison between the above collector currents. In other words, the collector current of the transistor 55 applied to a current mirror circuit forming the voltage/current comparing means 9 is converted into a current which has the same magnitude but the opposite sense, and the converted current is compared with the collector current of the transistor 35, so that a current indicative of a difference between these currents appears at the output terminal 3. The state when no current flows into and out of the output current 3 is the same as the state of the seventh embodiment when the voltage V2 at the input terminal 2 is equal to the reference voltage. This means that the amplifier comprising the two voltage/current converting means and the voltage/current comparing means also can have substantially the same effect as the seventh embodiment. In this way, even the eighth embodiment can have substantially the same effect as the the seventh embodiment. Shown in Fig. 8 is an arrangement of an amplifier in accordance with the ninth embodiment of the invention, which has substantially the same arrangement as the the seventh embodiment of Fig. 6 but with the resistor 23 in Fig. 6 removed. The operation of the ninth embodiment will then be explained. The operation of the ninth embodiment is substantially the same as that of the seventh embodiment. More specifically, in Fig. 6 showing the seventh embodiment, when the signal source impedance of the voltage source 1 connected to the input terminal 2 is sufficiently small as compared to the resistive value R22 of the resistor 22, the current flowing through the resistor 22 is determined by the voltage V1 of the voltage source 1. Thus, in the operation of the ninth embodiment, as in the operation of the seventh embodiment, the output current or voltage corresponding to a potential difference between the voltage V1 and the reference voltage V2 based on the equation (31) appears at the output terminal 3. At this time, the current flowing through the resistor 23 is supplied from the voltage source 1 and has a magnitude corresponding to the value of the voltage V1. Therefore, it will be seen that these elements do not contribute substantially to the operation of the amplifier. Thus, it will be appreciated that the ninth embodiment can have substantially the same effect as the seventh embodiment even when the resistor 23 is eliminated. However, in Fig. 6 showing the seventh embodiment, even when the voltage source 1 is not connected, the input terminal 2 has the same potential as the reference voltage V2; whereas, in Fig. 8 showing the ninth embodiment, the potential at the input terminal corresponds to the diode forward voltage. This difference appears in the form of such a phenomenon that, when the signal source impedance of the voltage source 1 is large, the voltage at the input terminal 2 is pulled in which direction from the no-load voltage value of the voltage source. However, the input terminal 4 has the same potential as the reference voltage V2. In this way, even the ninth embodiment can have substantially the same advantage as in the seventh embodiment, and can also have an additional advantage that the resistor 23 can be eliminated and thus the amplifier can be made with a simpler arrangement. Fig. 9 shows an arrangement of an amplifier in accordance with a tenth embodiment of the invention, which has substantially the same arrangement as the seventh embodiment of Fig. 6, except that the resistor 33 in Fig 6 is eliminated. The operation of the tenth embodiment will then be explained. The operation of the tenth embodiment is substantially the same as that of the seventh embodiment. More specifically, in Fig. 6, when the signal source impedance of the voltage source 5 connected to the input terminal 4 is sufficiently small as compared to the resistive value R32 of the resistor 32, the current flowing through the resistor 32 is determined by the voltage V1 of the voltage source 1. Thus, in the operation of the tenth embodiment, as in the operation of the seventh embodiment, the output current or voltage corresponding to a potential difference between the voltage V1 and the reference voltage V2 based on the equation (31) appears at the output terminal 3. At this time, the current flowing through the resistor 33 is supplied from the voltage source 1 and has a magnitude corresponding to the value of the voltage V5. Therefore, it will be seen that these elements do not contribute substantially to the operation of the amplifier. Thus, it will be appreciated that the tenth embodiment can have substantially the same effect as the seventh embodiment even when the resistor 33 is eliminated. However, in Fig. 6 showing the seventh embodiment, when the voltage source 5 is not connected, the input terminal 4 has the same potential as the reference voltage V2; whereas, in Fig. 9 showing the tenth embodiment, the potential at the input terminal corresponds to the diode forward voltage. This difference appears in the form of such a phenomenon that, when the signal source impedance of the voltage source 5 is large, the voltage at the input terminal 4 is pulled in which direction from the no-load voltage value of the voltage source. However, the input terminal 2 has the same potential as the reference voltage V2. In this way, even the tenth embodiment can have substantially the same advantage as in the seventh embodiment, and can also have an additional advantage that the resistor 33 can be eliminated and thus the amplifier can be made with a simpler arrangement. Fig. 10 shows an arrangement of an amplifier in accordance with an eleventh embodiment of the invention, which has substantially the same arrangement as the third embodiment of Fig. 2, except that the current sources 24 and 34 in Fig 2 are eliminated and the diode-connected transistor 25 is provided. The arrangement of Fig. 10 has substantially the same left-side and right-side structures having the same constants. That is, in the left- and right-side structures, the resistor 22 corresponds to the resistor 32, the resistor 23 corresponds to the resistor 33, the current source 21 corresponds to the voltage source 31, and the transistor 25 corresponds to the transistor 35, respectively. The operation of the eleventh embodiment will then be explained. The operation of the eleventh embodiment is substantially the same as that of the third embodiment. When both or either one of the input terminals 2 and 4 is open-circuited and the other input terminal has the same potential as the reference voltage, the left- and right-side circuits perform the similar operation. However, since the current source 24 and the current source 34 are not provided, the reference voltage must be set to be above the diode forward voltage. That is, the currents, which are supplied to the junction points A and B from the current sources 24 and 34 in the third embodiment, are set to be supplied from the current source 31 through the resistors 22 and 32. Even with such an arrangement, the reference voltage is the same as in the third embodiment and is expressed by the equation (25). In this way, when the reference voltage is set to be above the diode forward voltage, the eleventh embodiment can also have, in addition to the advantage of the third embodiment, an additional advantage that the voltage source 24 and the current source 34 can be eliminated and the eleventh embodiment can be made with a simpler arrangement. When the resistive value R252 is sufficiently smaller than the resistive value R22, the voltage V2 is expressed in the form of a ratio between the resistive values R22 and R23 independent of the absolute values of the resistive values and thus the circuit formation of the amplifier can be facilitated. Fig. 11 shows an arrangement of an amplifier in accordance with a twelfth embodiment of the invention, which comprises a first voltage/current converting means corresponding to the right-side similar circuit in Fig. 10 of the eleventh embodiment but with the transistor 35 removed; a second voltage/current converting means similar to the first one including an input terminal 4, resistors 42 and 43, a current source 41 and transistors 45 and 55; and a voltage/current comparing means 9 including transistors 6 and 7 and a voltage source 8. The amplifier of Fig. 11 also includes an output terminal 3. Explanation will next be made as to the operation of the twelfth embodiment. The operation of the first voltage/current converting means in the twelfth embodiment is the same as that of the left-side similar circuit having the same structure in Fig. 10 of the eleventh embodiment. The operation of the second voltage/current converting means is also the same as that of the above left-side similar circuit. The voltage V2 when no voltages are applied to the input terminals 2 and 4 is expressed by the equation (25) as in the 'eleventh embodiment. Assuming that the first and second voltage/current converting means have the same element constants and the same currents in their corresponding parts, the first and second voltage/current converting means also has the same voltages in their corresponding parts. This means that the first and second voltage/ current converting means perform the similar operation. The collector currents of the transistors 35 and 55 as the outputs of the first and second voltage/current converting means become the same, which results in that no current flows at the output terminal 3 of the current/voltage comparing means 9 for comparison between the above collector currents. In other words, the collector current of the transistor 55 applied to a current mirror circuit forming the voltage/current comparing means 9 is converted into a current which has the same magnitude but the opposite sense, and the converted current is compared with the collector current of the transistor 35, so that a current indicative of a difference between these currents appears at the output terminal 3. The state when no current flows into and out of the output current 3 is the same as the state of the eleventh embodiment when the voltage V2 at the input terminal 2 is equal to the reference voltage. This means that the amplifier comprising the two voltage/ current converting means and the voltage/current comparing means also can have substantially the same effect as the elevanth embodiment. In this way, even the twelfth embodiment can have substantially the same effect as the eleventh embodiment. Fig. 12A shows an arrangement of an amplifier in accordance with a thirteenth embodiment, which has substantially the same arrangement as the eleventh embodiment of Fig. 10, except that the resistor 23 in Fig 10 is eliminated. The operation of the thirteenth embodiment will then be explained. The operation of the thirteenth embodiment is substantially the same as that of the eleventh embodiment. More specifically, in Fig. 10 showing the eleventh embodiment, when the signal source impedance of the voltage source 1 connected to the input terminal 2 is sufficiently small as compared to the resistive value R22 of the resistor 22, the current flowing through the resistor 22 is determined by the voltage V1 of the voltage source 1. Thus, in the operation of the thirteenth embodiment, as in the operation of the eleventh embodiment, the output current or voltage corresponding to a potential difference between the voltage V1 and the reference voltage V2 based on the equation (25) appears at the output terminal 3. At this time, the current flowing through the resistor 23 is supplied from the voltage source 1 and has a magnitude corresponding to the value of the voltage V1. Therefore, it will be seen that these elements do not contribute substantially to the operation of the amplifier. Thus, it will be appreciated that the thirteenth embodiment can have substantially the same effect as the eleventh embodiment even when the resistor 23 is eliminated. However, in Fig. 10 showing the eleventh embodiment, when the voltage source 1 is not connected, the input terminal 2 has the same potential as the reference voltage V2; whereas, in Fig. 12A showing the thirteenth embodiment, the potential at the input terminal corresponds to the diode forward voltage. This difference appears in the form of such a phenomenon that, when the signal source impedance of the voltage source 1 is large, the voltage at the input terminal 2 is pulled in which direction from the no-load voltage value of the voltage source. However, the input terminal 4 has the same potential as the reference voltage V2. In this way, even the thirteenth embodiment can have substantially the same advantage as in the eleventh embodiment, and can also have an additional advantage that the resistor 23 can be eliminated and thus the amplifier can be made with a simpler arrangement. Fig. 12A shows an arrangement of an amplifier in accordance with a fourteenth embodiment, which has substantially the same arrangement as the thirteenth embodiment of Fig. 12A, except that the resistor 33 in Fig 12A is eliminated. The operation of the fourteenth embodiment will then be explained. The operation of the fourteenth embodiment is substantially the same as that of the thirteenth embodiment, except that the resistor 33 is not provided. However, the absence of the resistor 33 causes the setting of the reference voltage to be limited. That is, due to the absence of the resistor 33, the value of the reference voltage is expressed by the following equation (32) corresponding to the equation (25) of the third embodiment when the resistive value R33 of the resistor 33 is set to be infinite. V2 = Vf25 + (k x T/q) x ln(N) x (R22 + R252 + R252)/Rcs ∴ M = 1 In this way, although the setting range of the reference voltage is restricted, the fourteenth embodiment can also have, in addition to the advantage of the thirteenth embodiment, tion, an additional advantage that the resistor 33 can be eliminated and thus the fourteenth embodiment can be arranged with a simpler arrangement. When the reference voltage V2 is applied to the input terminal 2, even in the fourteenth embodiment, the input- and output-side circuits of the current mirror circuit perform the similar operation. However, since the terminal voltage of the current source 31 causes generation of the high reference voltage based on the equation (32), the power source voltage for driving of the amplifier cannot be lowered. Hence, when the establishment of the voltage similar operation is given up and the resistor 32 is eliminated, only the current similar operation can be established. Even this case can have the same reference voltage and effect as the fourteenth embodiment. However, this arrangement is exactly the same as the first embodiment. Thus, the first embodiment can be considered to be a modification of the third embodiment. Fig. 13 shows an arrangement of an amplifier in accordance with a fifteenth embodiment, which has substantially the same arrangement as the eleventh embodiment of Fig. 10 but with the resistor 33 in Fig. 10 removed. The operation of the fifteenth embodiment will then be explained. The operation of the fifteenth embodiment is substantially the same as that of the eleventh embodiment. More specifically, in Fig. 10 showing the eleventh embodiment, when the signal source impedance of the voltage source 5 connected to the input terminal 4 is sufficiently small as compared to the resistive value R32 of the resistor 32, the current flowing through the resistor 32 is determined by the voltage V5 of the voltage source 5. Thus, in the operation of the fifteenth embodiment, as in the operation of the eleventh embodiment, the output current or voltage corresponding to a potential difference between the voltage V1 and the reference voltage V2 based on the equation (25) appears at the output terminal 3. At this time, the current flowing through the resistor 33 is supplied from the voltage source 5 and has a magnitude corresponding to the value of the voltage V5. Therefore, it will be seen that these elements do not contribute substantially to the operation of the amplifier. Thus, it will be appreciated that the fifteenth embodiment can have substantially the same effect as the eleventh embodiment even when the resistor 33 is eliminated. However, in Fig. 10 showing the eleventh embodiment, when the voltage source 5 is not connected, the input terminal 4 has the same potential as the reference voltage V2; whereas, in Fig. 13 showing the fifteenth embodiment, the potential at the input terminal corresponds to the diode forward voltage. This difference appears in the form of such a phenomenon that, when the signal source impedance of the voltage source 5 is large, the voltage at the input terminal 4 is pulled in which direction from the no-load voltage value of the voltage source. However, the input terminal 2 has the same potential as the reference voltage V2. In this way, even the fifteenth embodiment can have substantially the same advantage as in the eleventh embodiment, and can also have an additional advantage that the resistor 33 can be eliminated and thus the amplifier can be made with a simpler arrangement. In the third to fifteenth embodiments, the junction B has been connected directly to the output terminal 3. However, such an arrangement may be employed that the transistor 15 and the current source 16 are added to extract from the junction point B a current having the same magnitude as the base current of the transistors 25 and 35 as in the second embodiment, whereby the influences of the base current of the transistors 25 and 35 at the junction point A is compensated for. Further, another suitable method for eliminating the influences of the base current may be employed so long as a current having the same magnitude as the base current of the transistors and extracted from the junction point A can be eventually extracted from the junction point B. Although the similar circuits as the input and output parts of the current mirror circuit have been set to have the same current values in the described embodiments, the current ratio between the input and output of the current mirror circuit may be set at a value R other than 1 and the currents of the similar circuits may be set to have the same as the value R. When the value R is set to be large, the output current at the output terminal 3 becomes large and its load driving ability can be advantageously enhanced. Though the input and output current values of the current mirror circuit of the current comparing means 9 including the transistors 6 and 7 are set to be equal to each other in the fourth, eighth and twelfth embodiments, the input/output current ratio of the current mirror circuit may be set to be a value R other than 1 and the current ratio between the currents of the similar circuits of the first and second voltage/ current converting means may be set to be equal to the same value R. When the value R is set to be large, the output current at the output terminal 3 becomes large and its load driving ability can be advantageously enhanced. Further, the current value of the current source is proportional to the absolute temperature T and inversely proportional to the set resistance Rcs in the described embodiments, but the current source may have arbitrary characteristics. In the latter case, the influences caused by variations and fluctuations in the reference voltage, temperature and power source voltage provide characteristics different from those in these embodiments. Though the current mirror circuit comprises bipolar transistors in the described embodiments, the current mirror circuit may comprise any elements. In the latter case, the temperature characteristic of the reference voltage becomes different from the former case due to the elements. Although a D.C. signal is used as the input signal in the described embodiments, an A.C. signal may be used as the input signal. The latter case is advantageous in that, when the A.C. signal is supplied through a coupling capacitor, in particular, the third, fourth, seventh, eighth, eleventh and twelfth embodiments, are operated so that the D.C. potential at the input terminal 2 causes the similar operation, whereby the need for newly adding a bias circuit can be eliminated. In the described embodiments, the lowest power source voltage necessary for operating the amplifier corresponds to an addition of the terminal voltages of the current sources to about 0.2V. Accordingly, when the reference voltage is set to be lower than the voltage of the input terminal of the current mirror circuit, the power source voltage can be set to be low. In addition, since the resistors included in the described embodiments are expressed in the form of a ratio between their resistive values in the equation indicative of the reference voltage, the accuracy of the absolute values of their resistors is not so important and mainly its relative accuracy becomes vital. Thus, these embodiments can be easily made advantageously in the form of a semiconductor integrated circuit, respectively.

Claims: An amplifier capable of operating with a low input voltage supplied thereto and independently of ambient temperature comprising: current mirror circuit means (12, 13); resistor means (11) connected to said current mirror circuit means and to an input of said amplifier; and current generating means (14) connected to said current mirror circuit means and to an output of said amplifier, characterized in that, in operation, a voltage drop across said resistor means is superimposed upon an input potential of said current mirror circuit means to produce a reference voltage at the input (2) of said amplifier. An amplifier according to claim 1, characterized in that said current mirror circuit means includes a current mirror circuit (12, 13); said resistor means includes a resistor (11) having one end thereof connected to an input of said current mirror circuit (12, 13) and the other end thereof connected to the input (2) of said amplifier; and said current generating means includes a current generating circuit (14) connected to an output of said current mirror circuit (12, 13). An amplifier according to claim 1, characterized in that said current mirror circuit means includes a current mirror circuit (12, 13); said resistor means includes a resistor (11) having one end thereof connected to an input of said current mirror circuit (12, 13) and the other end thereof connected to the input (2) of said amplifier; and said current generating means includes first and second current generating circuits (14; 16), said first current generating circuit (14) being connected to an output of said current mirror circuit (12, 13), and said second current generating circuit (16) being connected to an output of a transistor (15) which has an input connected to the output of said current mirror circuit (12, 13). An amplifier according to claim 1, characterized in that said current mirror circuit means includes a current mirror circuit (25, 35); said resistor means includes first and second voltage division circuits (22, 23; 32, 33), said first voltage division circuit (22, 23) being connected to an input of said current mirror circuit (25, 35), and said second voltage division circuit (32, 33) being connected to an output of said current mirror circuit (25, 35); and said current generating means includes first, second, third and fourth current generating circuits (21; 24; 31; 34), said first current generating circuit (21) being connected to a division output of said first voltage division circuit (22, 23), the division output of which is connected to a first input (2) of said amplifier, said second current generating circuit (24) being connected to the input of said current mirror circuit (25, 35), said third current generating circuit (31) being connected to a division output of said second voltage division circuit (32, 33), the division output of which is connected to a second input (4) of said amplifier, and said fourth current generating circuit (34) being connected to the output of said current mirror circuit (25, 35). An amplifier according to Claim 1 characterized in that said current mirror circuit means includes first and second current mirror circuit (25, 35; 45, 55); said resistor means includes first and second voltage division circuit (22, 23; 42, 43), said first voltage division circuit (22, 23) being connected to an input of said first current mirror circuit (25, 35), a division output of said first voltage division circuit (22, 23) being connected to a first input (2) of said amplifier, and said second voltage division circuit (42, 43) being connected to an input of said second mirror circuit (45, 55), a division output of said second voltage division circuit (42, 43) being connected to a second input (4) of said amplifier; said current generating means includes first, second, third and fourth current generating circuits (21; 24; 41; 44), said first current generating circuit (21) being connected to the division output of said first voltage division circuit (22, 23), said second current generating circuit (24) being connected to the input of said first current mirror circuit (25, 35), said third current generating circuit (41) being connected to the division output of said second voltage division circuit (42, 43), and said fourth current generating circuit (44) being connected to the input of said second mirror circuit (45, 55), and characterized by further comprising: current comparing means (9) for comparing an output current of said first current mirror circuit (25, 35) with that of said second mirror circuit (45, 55). An amplifier according to Claim 1 characterized in that said current mirror circuit means includes a current mirror circuit (25, 35); said resistor means includes a resistor (22) and a voltage division circuit (32, 33), said resistor (22) having one end thereof connected to an input of said current mirror circuit (25, 35) and the other end thereof connected to a first input (2) of said amplifier, and said voltage division circuit (32, 33) being connected to an output of said current mirror circuit (25, 35); and said current generating means includes first, second and third current generating circuits (24; 31; 34), said first current generating circuit (24) being connected to the input of said current mirror circuit (25, 35), said second current generating circuit (31) being connected to a division output of said voltage division circuit (32, 33), the division output of which is connected to a second input (4) of said amplifier, and said third current generating circuit (34) being connected to the output of said current mirror circuit (25, 35). An amplifier according to Claim 1 characterized in that said current mirror circuit means includes a current mirror circuit (25, 35); said resistor means includes a voltage division circuit (22, 23) and a resistor (32), said first voltage division circuit (22, 23) being connected to an input of said current mirror circuit (25, 35), and said resistor (32) having one end thereof connected to an output of said current mirror circuit (25, 35) and the other end thereof connected to a second input (4) of said amplifier; and said current generating means includes first, second and third current generating circuits (21; 24; 34), said first current generating circuit (21) being connected to a division output of said voltage division circuit (22, 23), the division output of which is connected to a first input (2) of said amplifier, said second current generating circuit (24) being connected to the input of said current mirror circuit (25, 35), and said third current generating circuit (34) being connected to the output of said current mirror circuit (25, 35). An amplifier according to Claim 1 characterized in that said current mirror circuit means includes a current mirror circuit (25, 35); said resistor means includes first and second voltage division circuits (22, 23; 32, 33), said first voltage division circuit (22, 23) being connected to an input of said current mirror circuit (25, 35), a division output of said first voltage division circuit (22, 23) being connected to a first input (2) of said amplifier, and said second voltage division circuit (32, 33) being connected to an output of said current mirror circuit (25, 35), a division output of said second voltage division circuit (32, 33) being connected to a second input (4) of said amplifier; and said current generating means includes first and second current generating circuits (24; 34), said first current generating circuit (24) being connected to the input of said current mirror circuit (25, 35), and said second current generating circuit (34) being connected to the output of said current mirror circuit (25, 35). An amplifier according to Claim 1 characterized in that said current mirror circuit means includes first and second current mirror circuit (25, 35; 45, 55); said resistor means includes first and second voltage division circuit (22, 23; 42, 43), said first voltage division circuit (22, 23) being connected to an input of said first current mirror circuit (25, 35), a division output of said first voltage division circuit (22, 23) being connected to a first input (2) of said amplifier, and said second voltage division circuit (42, 43) being connected to an input of said second current mirror circuit (45, 55), a division output of said second voltage division circuit (42, 43) being connected to a second input (4) of said amplifier; said current generating means includes first and second current generating circuit (24; 44), said first current generating circuit (24) being connected to the input of said first current mirror circuit (25, 35), and said second current generating circuit (44) being connected to the input of said second mirror circuit (45, 55), and characterized by further comprising: current comparing means (9) for comparing an output current of said first current mirror circuit (25, 35) with that of said second mirror circuit (45, 55). An amplifier according to Claim 1 characterized in that said current mirror circuit means includes a current mirror circuit (25, 35); said resistor means includes a resistor (22) and a voltage division circuit (32, 33), said resistor (22) having one end thereof connected to an input of said current mirror circuit (25, 35) and the other end thereof connected to a first input (2) of said amplifier, and said voltage division circuit (32, 33) being connected to an output of said current mirror circuit (25, 35), a division output of said voltage division circuit (32, 33) being connected to a second input (4) of said amplifier; and said current generating means includes first and second current generating circuits (24; 34), said first current generating circuit (24) being connected to the input of said current mirror circuit (25, 35), and said second current generating circuit (34) being connected to the output of said current mirror circuit (25, 35). An amplifier according to Claim 1 characterized in that said current mirror circuit means includes a current mirror circuit (25, 35); said resistor means includes a voltage division circuit (22, 23) and a resistor (32), said voltage division circuit (22, 23) being connected to an input of said current mirror circuit (25, 35), a division output of said voltage division circuit (22, 23) being connected to a first input (2) of said amplifier, and said resistor (32) having one end thereof connected to an output of said current mirror circuit (25, 35) and the other end thereof connected to a second input (4) of said amplifier; and said current generating means includes first and second current generating circuits (24; 34), said first current generating circuit (24) being connected to the input of said current mirror circuit (25, 35), and said second current generating circuit (34) being connected to the output of said current mirror circuit (25, 35). An amplifier according to Claim 1 characterized in that said current mirror circuit means includes a current mirror circuit (25, 35); said resistor means includes first and second voltage division circuits (22, 23; 32, 33), said first voltage division circuit (22, 23) being connected to an input of said current mirror circuit (25, 35), a division output of said first voltage division circuit (22, 23) being connected to a first input (2) of said amplifier, and said second voltage division circuit (32, 33) being connected to an output of said current mirror circuit (25, 35), a division output of said second voltage division circuit (32, 33) being connected to a second input (4) of said amplifier; and said current generating means includes first and second current generating circuits (21; 31), said first current generating circuit (21) being connected to the division output of said first voltage division circuit (22, 23), and said second current generating circuit (31) being connected to the division output of said second voltage division circuit (32, 33). An amplifier according to Claim 1 characterized in that said current mirror circuit means includes first and second current mirror circuit (25, 35; 45, 55); said resistor means includes first and second voltage division circuit (22, 23; 42, 43), said first voltage division circuit (22, 23) being connected to an input of said first current mirror circuit (25, 35), a division output of said first voltage division circuit (22, 23) being connected to a first input (2) of said amplifier, and said second voltage division circuit (42, 43) being connected to an input of said second mirror circuit (45, 55), a division output of said second voltage division circuit (42, 43) being connected to a second input (4) of said amplifier; said current generating means includes first and second current generating circuit (21; 41), said first current generating circuit (21) being connected to the division output of said first voltage division circuit (22, 23), and said second current generating circuit (41) being connected to the division output of said second voltage division circuit (42, 43), and characterized by further comprising: current comparing means (9) for comparing an output current of said first current mirror circuit (25, 35) with that of said second mirror circuit (45, 55). An amplifier according to Claim 1 characterized in that said current mirror circuit means includes a current mirror circuit (25, 35); said resistor means includes a resistor (22) and a voltage division circuit (32, 33), said resistor (22) having one end thereof connected to an input of said current mirror circuit (25, 35) and the other end thereof connected to a first input (2) of said amplifier, and said voltage division circuit (32, 33) being connected to an output of said current mirror circuit (25, 35), a division output of said voltage division circuit (32, 33) being connected to a second input (4) of said amplifier; and said current generating means includes a current generating circuit (31) connected to the division output of said voltage division circuit (32, 33). An amplifier according to Claim 1 characterized in that said current mirror circuit means includes a current mirror circuit (25, 35); said resistor means includes a first resistor (22) and a second resistor (32), said first resistor (22) having one end thereof connected to an input of said current mirror circuit (25, 35) and the other end thereof connected to a first input (2) of said amplifier, and said second resistor (32) having one end thereof connected to the output of said current mirror circuit (25, 35); and said current generating means includes a current generating circuit (31) connected to the other end of said resistor (32). An amplifier according to Claim 1 characterized in that said current mirror circuit means includes a current mirror circuit (25, 35); said resistor means includes a voltage division circuit (22, 23) and a resistor (32), said voltage division circuit (22, 23) being connected to an input of said current mirror circuit (25, 35), a division output of said voltage division circuit (22, 23) being connected to a first input (2) of said amplifier, and said resistor (32) having one end thereof connected to an output of said current mirror circuit (25, 35) and the other end thereof connected to a second input (4) of said amplifier; and said current generating means includes a current generating circuit (21), said current generating circuit (21) being connected to the division output of said voltage division circuit (22, 23).

Inventors: IKEDA MASAHARU, IKEDA, MASAHARU
Applicants: MATSUSHITA ELECTRIC IND CO LTD, MATSUSHITA ELECTRIC INDUSTRIAL CO., LTD.
Application year: 1992
Main classification: H03F3
IPC codes: G05F3