Semiconductor circuits

Abstract: It is an object of the present invention to provide an amplifier circuit for amplifying the voltage amplitude of a small amplitude signal to the CMOS level which operates at a high speed with low power dissipation while assuring high gain. PMOS FETs M₁₁, M₁₆ for pulling up the output are of the source-driving type and receive signals V IN1 , V IN1i , respectively, and NMOS FETs M₁₂, M₁₇ for pulling down the output are of the gate-driving type and receive level shifted signals V IN2 , V IN2i , respectively. In the circuit of the present invention, constant voltages for reference are set by diodes D₁₃, D₁₄, and bipolar transistors are connected as transistors for driving an output portion of the amplifier circuit. The performance of the amplifier circuit of the invention when it is used as a sensing amplifier to drive a TTL output is improved such that amplification gain is as high as two to five times and the response time/consumed current product is as low as one fifth to one tenth as compared with a conventional amplifier circuit.

Description: 1. Field of the Invention This invention relates to a semiconductor circuit, and more particularly to an amplifier circuit for amplifying a voltage signal. 2. Description of the Related Art Conventional amplifier circuits are utilized in various portions of semiconductor circuits. Fig. 1 is a circuit diagram showing an example of a conventional level-shifting circuit for shifting the level of a signal from the ECL level to the CMOS level. Referring to Fig. 1, input ECL signal V IN is inputted to the base of bipolar transistor Q 21 , and the emitter terminal of transistor Q 21 is grounded to the lowest potential (hereinafter referred to as ground potential) GND by way of current source I 21 , thereby constituting emitter follower circuit EF21. Output signal V IN1 of emitter follower circuit EF21 is inputted to level-shifting circuit LC21. Signal V IN1 is inputted to the gate of a P-type MOS field effect transistor (hereinafter referred to as a PMOS FET) M 21 , the source of which is connected to the highest potential (hereinafter referred to as the power supply voltage) V CC . The drain of PMOS FET M 21 is connected to the drain and the gate of an N-type MOS field effect transistor (hereinafter referred to as a NMOS FET) M 23 . The source of NMOS FET M 23 is connected to ground potential GND, and the gate of NMOS FET M 23 is connected commonly to the gate of NMOS FET M 24 , whereby an NMOS current mirror circuit is constituted from NMOS FETs M 23 and M 24 . Input signal V IN1 is inputted also to the source of PMOS FET M 22 , the drain of which is connected to the drain of NMOS FET M 24 , whereby a CMOS inverter is constituted from MOS FETs M 22 and M 24 . The drain terminals of PMOS FET M 22 and NMOS FET M 24 make an output terminal of level-shifting circuit LC21. Constant voltage V R21 for establishing a reference is applied to the gate of PMOS FET M 22 . In operation, signal V IN1 is level shifted by emitter follower circuit EF21 to a suitable input level voltage which normally presents a high level V CC - V f or a low level V CC - V f - ΔV, where V f is a forward voltage of the pn junction and is about 0.8 V, and ΔV is a signal amplitude and is about 0.5 to 1.5 V. When the level of signal V IN1 is changed to the low level, PMOS FET M 21 and NMOS FET M 24 are turned ON via the NMOS current mirror circuit, but PMCS FET M 22 is turned OFF when V R21 is equal to V CC - V f - ΔV - V TP , where V TP is the threshold voltage level of the PMOS FETs. The threshold voltage level of NMOS FETs is represented by V TN . Consequently, output signal out of the drains of PMOS FET M 22 and NMOS FET M 24 drops to the ground potential GND. On the other hand, when the level of signal V IN1 is changed to the high level if voltage V f is V f = V TP , PMOS FET M 21 and NMOS FETs M 23 and M 24 are turned OFF, and PMOS FET M 22 is turned ON. Consequently, output signal V out rises to V out = V IN1 = V CC - V f (refer to ISSCC Digest Of Technical Papers, 1989, p32). Fig. 2 is a circuit diagram of an example of a conventional sensing amplifier circuit for amplifying a read-out small amplitude signal of a memory circuit. Referring to Fig. 2, input signal V INO which is an operating input signal and another signal V INOi which is opposite in phase to signal V INO are signals having an amplitude of approximately 0.5 to 2 V. Signal V INO is received by the gate of PMOS FET M 31 , and opposite phase signal V INOi is received by the gate of PMOS FET M 32 . A pair of NMOS FETs, M 33 and M 34 , which form a current mirror circuit are connected to the drains of PMOS FETs M 31 and M 32 , respectively. Here, the NMOS FET M 33 side serves for current monitoring while the NMOS FET M 34 side serves for driving, and the CMOS outputs of PMOS FET M 32 and NMOS FET M 34 produce output signal V out . A similar circuit wherein the inputs of signals V INO and V INOi to the PMOS gates are reversed is formed from PMOS and NMOS FETs M 35 to M 38 and the output of the circuit is signal V outi , which is opposite in phase to signal V out . A PMOS FET to which an input signal of the low level is inputted is turned up, but a PMOS FET to which an input signal of the high level is inputted is either turned ON at a low level or is turned OFF. Since the level to which PMOS FETs M 31 and M 35 are turned ON is transmitted in proportion to the level to which NMOS FETs M 34 and M 38 are turned ON due to an effect of the NMOS current mirror circuit, when the level of signal V INO is high and the level of opposite phase signal V INOi is low, output signal V out is raised to V out = V CC by PMOS FET M 32 while opposite phase signal V outi is lowered to V outi = GND by NMOS FET M 38 . This similarly applies in cases in which the inputs are reversed. Various modifications have also been reported including a sensing amplifier circuit of the same type wherein the transistor which receives an input signal at the gate thereof is formed from an NMOS FET or the current mirror circuit is formed from PMOS FETs (refer to the ISSCC 1990 Digest Of Technical Papers 1990, P134). In the conventional amplifier circuits described above, since a current mirror circuit is employed, when high-speed operation is required, the responding speed of the current mirror circuit must be high. To this end, the capacities to which the transistors are turned ON on the raising side and the lowering side for receiving input signals must be raised. While the turning on capacity can be raised by adjusting the voltage of the input signal to increase the gate voltage, the turning off capacity is also increased simultaneously, and this results in the increase of through currents and the reduction of the turning ON/OFF ratio. This causes saturation in the increase of the speed and the reduction of the voltage margin arising from an increase of power consumption and a decrease of the amplifying capacity (gain). This is becoming a serious problem in designing high-speed integrated circuits. Further, in the conventional circuits described above, if the types and/or the switching operation types of the transistors on the raising side and the lowering side for receiving input signals are different, individually optimum input voltages are involved. However, in actual use, signals are inputted at the same voltage to the transistors, and as a result, the conventional circuits fail to exhibit sufficient device performance. The problems described above are expected to become more serious with the development of larger scale, high-speed integrated circuits. EP-A-0 417 786 discloses a level shift circuit which includes an output differenting pair of transistors as an input circuit section, which are switchingly operated in accordance with the level of an input signal supplied from a preceding circuit and an output circuit section composed of first and second emitter follower transistors. A third transistor has its current path connected at one end to an emitter of the first emitter follower transistor and makes an output level of the first emitter follower transistor at a predetermined level. A fourth transistor has its current path connected at one end to the other end of the third transistor and is driven by an output voltage of the second emitter follower transistor to allow an ouput level of the first emitter follower transistor to be shifted to a low level. An inverter circuit is connected to the outputs of the first and second emitter follower transistors and composed of a P- and N-channel transistors commonly connected at their adjacent paths to each other. The inverter circuit is operated in accordance with an output level of the first emitter follower transistor to allow an output level of the second emitter follower transistor to be output from that common connection point. Additionally, DE-40 10 145 C1 discloses a semiconductor circuit according to the precharacterizing part of claim 1 and 2. According to this document the second signal is downward level shifted a means of a transistor. SUMMARY OF THE INVENTION According to an aspect of the present invention there is provided a new semiconductor circuit receiving an input signal of a first amplitude and amplifying the input signal into an output signal of a second amplitude. This object is achieved according to the present invention by a semiconductor circuit as defined in claims 1 or 2. The dependent claims are related to further advantageous aspects of the present invention. It is an advantage of the present invention to provide a semiconductor circuit which is free from deterioration of the turning ON/OFF capacity ratio arising from an increase of through currents. It is another advantage of the present invention to provide a semiconductor circuit which has a high amplifying capacity and is capable of operating at a high speed with low power consumption. According to a further aspect of the present invention, there is provided a semiconductor circuit of the ECL input type, wherein the semiconductor circuit described above is employed as a level-shifting circuit for amplifying a signal from an ECL input level to approximately the power supply voltage for CMOS or TTL. According to a still further aspect of the present invention, there is provided a semiconductor circuit, wherein the semiconductor circuit described above is employed as a sensing amplifier circuit which amplifies a signal from an internal low voltage which is approximately as high as the ECL level to approximately the power supply voltage for the TTL level output or alternatively employed as an output buffer circuit for driving an output transistor. Other and further objects and aspects of the invention will be obvious after explanation of the illustrative embodiments that will now be described or that will be indicated in the appended claims, and various advantages not referred to herein will be obvious to those skilled in the art upon employment of the invention in practice. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a circuit diagram showing an example of a conventional level-shifting circuit; Fig. 2 is a circuit diagram showing an example of a conventional sensing amplifier circuit; Fig. 3 is a circuit diagram showing a first embodiment of the present invention; Fig. 4 is a circuit diagram showing a second embodiment of the present invention; Fig. 5 is a circuit diagram showing a first comparative example of a semiconductor circuit; Fig. 6 is a circuit diagram showing a second comparative semiconductor circuit; Fig. 7 is a circuit diagram showing a third comparative semiconductor circuit; Fig. 8 is a circuit diagram showing a fourth comparative semiconductor circuit; Fig. 9 is a circuit diagram showing a fifth comparative semiconductor circuit. Fig. 10 is a circuit diagram showing a sixth comparative semiconductor circuit; Fig. 11 is a circuit diagram showing a seventh comparative semiconductor circuit; Fig. 12 is a circuit diagram showing a eigth comparative semiconductor circuit; Fig. 13 is a circuit diagram showing a ninth comparative semiconductor circuit; Fig. 14A is a diagram of the DC characteristics showing variations of output signal voltages with respect to input signal difference voltages in a semiconductor circuit of the present invention and a conventional semiconductor circuit; Fig. 14B is a diagram of DC characteristics showing variations of DC through current consumption with respect to input signal difference voltages in a semiconductor circuit of the present invention and a conventional semiconductor circuit; Fig. 15 is a diagram of DC characteristics showing amplifier gain with respect to input amplitude in a semiconductor circuit of the present invention; and Fig. 16 is a characteristic diagram showing speed with respect to current consumption of an amplifier circuit until a TTL output is obtained when an output transistor of a semiconductor circuit of the present invention is driven. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The preferred embodiments of the present invention will now be described with reference to the drawings. Fig. 3 shows in a circuit diagram a semiconductor circuit of a first preferred embodiment of the present invention. Referring to Fig. 3, input signal V IN is inputted to the base of bipolar transistor Q 41 in emitter follower circuit EF41. The emitter terminal of bipolar transistor Q 41 is connected to the anode of pn junction type diode D41, and the cathode of diode D 41 is grounded to the ground potential GND by way of current source I 41 . Output signals V IN1 and V IN2 of emitter follower circuit EF41 are inputted to level-shifting circuit LC41. Here, signal V IN1 has a level shifted down by pn junction forward voltage V f from signal V IN , and signal V IN2 has another level shifted down by 2V f from signal V IN . In level-shifting circuit LC41, signal V IN2 is inputted to the gate of PMOS FET M 41 . The source of PMOS FET M 41 is connected to the power supply voltage V CC , and the drain of PMOS FET M 41 is connected to the drain and the gate of NMOS FET M 43 , the source of which is connected to the ground potential GND. The gate of NMOS FET M 43 is also connected to the gate of NMOS FET M 44 , and an NMOS current mirror circuit is constituted from NMOS FETs M 43 and M 44 . Input signal V IN1 is inputted to the source of PMOS FET M 42 and the drain of PMOS FET M 42 is connected to the drain of NMOS FET M 44 , thereby constituting a CMOS inverter. The common drains of PMOS FET M 42 and NMOS FET M 44 provide output signal V out of level-shifting circuit LC41. Constant voltage V R41 for reference is applied to the gate of PMOS FET M 42 . In operation, when it has, for example, an ECL amplitude of small amplitude, input signal V IN to emitter follower circuit EF41 presents a high level equal to the power supply voltage V CC or a low level equal to V CC - ΔV, where ΔV is an amplitude of the input signal. The input levels of signals V IN1 and V IN2 are given by equations (1) to (4) below: VIN1 (H) = V CC - V f = 4.2 V VIN1 (L) = V CC - V f - ΔV = 2.7 V VIN2 (H) = V CC - 2V f = 3.4 V VIN2 (L) = V CC - 2V f - ΔV = 1.9 V where V CC = 5 V, V f = 0.8 V, and ΔV = 1.5 V. Since signal V IN1 is inputted to the source of PMOS FET M 42 for pull-up of signal V out , the capacity of PMOS FET M 42 can be controlled by adjusting the level of voltage V R41 . In order to maximize the difference between the turning on and off capacities, the level of voltage V R41 should be equal to V IN1 (L) - V TP . The response from the input to the output is comparatively high in speed since only one stage of the MOS gate is involved, and in order to further raise the speed, the level of voltage V R41 should be lowered although the through current of PMOS FET M 42 increases. The factor which determines the speed of level-shifting circuit LC41 is the turning ON/OFF of PMOS FET M 41 . In the conventional circuit shown in Fig. 1, signal V IN1 is inputted to the gate of PMOS FET Q 21 , which corresponds to PMOS FET M 41 , and gate voltage V G for controlling the turning on capacity of PMOS FET M 21 when the input level is low is V G = -V f - ΔV = -2.3 V. On the other hand, in the circuit of the present embodiment wherein signal V IN2 is inputted to the gate of PMOS FET M 41 , gate voltage V G is V G = -2V f - ΔV = -3.1 V, and consequently, the turning on capacity is twice or more the turning on capacity of the conventional circuit. If the capacity of PMOS FET M 41 is raised by adjusting the left shift amount which is provided by diode D 41 in emitter follower circuit EF 41 , even though the through current increases when it is in the OFF state, the size of PMOS FET M 41 can be decreased so that the response of the NMOS current mirror circuit can be increased in speed. Operation from the input to the output will be described subsequently. When signals V IN1 and V IN2 are both at the low level, PMOS FET M 42 is OFF while PMOS FET M 41 is ON and NMOS FET M 44 is ON, and consequently, signal V out drops. In contrast, when signals V IN1 and V IN2 are at the high level, PMOS FET M 42 is ON while PMOS FET M 42 is OFF and NMOS FET M 44 is OFF, and consequently, signal V out rises. Accordingly, the rising and dropping responding speeds of output signal V out can be raised to their optimal values within the range permitted by the through current by adjusting the level of voltage V R41 and the input level shift amount (= V IN1 - V IN2 ), respectively. In this instance, since output level V out (H) is equal to V out (H) = V CC - V f and output level V out (L) is equal to 0, there is no problem with a CMOS input system circuit at the next stage. If a circuit is designed with a consumed current substantially the same as in conventional circuits (about 0.3 to 0.5 mA) using the present circuit arrangement, the speed can be improved by about 20 to 30%. Fig. 4 shows in circuit diagram a semiconductor circuit of a second preferred embodiment of the present invention which is a modification to the semiconductor circuit of the first embodiment. Here in the present semiconductor circuit, PMOS FET M 51 which receives the input of signal V IN1 at the source thereof is connected as a pull-down transistor for output signal V out to emitter follower circuit EF41, and PMOS FET M 52 which receives the input of signal V IN2 at the gate thereof is connected as a pull-up transistor for output signal V out to emitter follower circuit EF41. Constant voltage V R51 for reference is applied to the gate of PMOS FET M 51 . In the present circuit arrangement, when input signal V IN is at the high level, output signal V out presents the low level, but when input signal V IN is at the low level, output signal V out presents the high level. Thus, the present circuit arrangement realizes the reverse logic to that of the circuit arrangement of the first embodiment. An example of a first comparative semiconductor circuit is shown in the circuit diagram of Fig. 5. As shown in Fig. 5, the semiconductor circuit does not employ a current mirror circuit but is in the form of a mere amplifier circuit wherein PMOS FET M 61 and NMOS FET M 62 are connected to a CMOS inverter. Input signal V IN1 is inputted to the source of PMOS FET M 61 , and constant voltage V R61 is applied to the gate of PMOS FET M 61 . Another input signal V IN2i which is level shifted from input signal V IN1 and is opposite in phase is inputted to the gate of NMOS FET M 62 , and another constant voltage V R62 is applied to the source of NMOS FET M 62 . In operation, when signal V IN1 is at the high level and opposite phase signal V IN2i is at the low level, PMOS FET M 61 is ON and NMOS FET M 62 is OFF, and consequently, output signal V out rises to V out = V IN1 . When signal V IN1 is at the low level and opposite phase signal V IN2i is at the high level, PMOS FET M61 is OFF and NMOS FET M 62 is ON, and consequently, output signal V out drops to V out = V R62 . Here, when signals V IN1 and V IN2 have the values given by equations (1) to (4) above, the high and low levels of the gate voltage V G which rises and drops with the high and low levels of signal V IN1 to PMOS FET M 61 are given by following equations (5) and (6), respectively: V G (M 61 : H) = V CC - V f - V R61 V G (M 61 : L) = V CC - V f - ΔV - V R61 Similarly, the high and low levels of the gate voltage V G which rises and drops with the high and low levels of signal V IN2 to NMOS FET M 62 are given by following equations (7) and (8), respectively: V G (M 62 : H) = V CC - 2V f - V R62 V G (M 62 : L) = V CC - 2V f - ΔV - V R62 According to the present embodiment, by designing the turning ON/OFF capacity ratio of each transistor to its maximum value, a maximum amplifier gain can be obtained in a condition wherein the flow of the through current is nearly eliminated. To this end, the gate voltages V G when the transistors are OFF should be set to threshold value V TP of the PMOS transistor and V TN of the NMOS transistor, and accordingly, V G (M 62 : H) = V CC - V f - ΔV - V R61 = -V TP V G (M 62 : L) = V CC - 2V f - ΔV - V R62 = -V TN Thus, if constant voltages V R61 and V R62 for reference are calculated from the equations (9) and (10) above, they are given by equations (11) and (12) below, respectively: V R61 = V CC - V f - ΔV + V TP = 5 - 0.8 - 1.5 - 1.6 = 1.1 V R62 = V CC - 2V f - ΔV + V TP = 5 - 1.6 - 1.5 - 1.6 = 0.9 A back bias effect arising from the difference between the substrate potential and the source potential is taken into consideration in equation (11) and (12) given above, while the threshold valves of the MOS transistors are considered to be V TP = 0.8 V and V TN = 0.8 V if the source voltage is equal to the substrate potential. By setting voltages V R61 and V R62 in this manner, output signal V out presents the levels of H = V IN1 (H) = V CC - 0.8 V and L = V R62 = 0.9 V, which are considered to be sufficient levels for inputting to a CMOS FET at the next stage. The responding time of the semiconductor circuit of this comparative example is decreased to about one half that of conventional semiconductor circuits which employ an NMOS current mirror circuit, and the through current is decreased to about 10 to 30%. In the circuit diagram of Fig. 6 is shown a second comparative semiconductor circuit which is a simplified form of the semiconductor circuit shown in Fig. 5. In the present semiconductor circuit, only one constant voltage for reference is involved which is applied as voltage V R71 both to the gate of PMOS FET M 71 and the source of NMOS FET M 72 . As indicated by equations (11) and (12) above, reference levels for PMOS FET M 71 and NMOS FET M 72 can be made substantially equal to each other by suitably adjusting the two input signals V IN1 and V IN2i . In short, constant voltage V R71 for reference should be equal to V R71 = 1 V, by which a necessary signal system can be simplified. Similarly, Fig. 7 shows in circuit diagram a third comparative semiconductor circuit wherein input signals V IN1 and V IN2i are inputted at voltages determined from the ground potential GND, similar to the second comparative semiconductor circuit described above. The present semiconductor circuit is different from the semiconductor circuit shown in Fig. 6 only in that voltage V R81 is applied and PMOS FET M 81 and NMOS FET M 82 are handled reversely to the PMOS FET M 71 and NMOS FET M 72 in the semiconductor circuit shown Fig. 6. The present semiconductor circuit indicates that the concept of the present invention can be applied to a semiconductor circuit which receives an input signal other than an ECL input such as when the potentials of input signals V IN1 and V IN2i are low. Fig. 8 shows in circuit diagram a fourth comparative semiconductor circuit. Referring to Fig. 8, the semiconductor circuit shown is an amplifier circuit for outputting output signal V out with a full amplitude from the power supply voltage V CC to the ground potential GND. Input signals V IN1 and V IN2i , PMOS FET M 71 , NMOS FET M 72 and constant voltage V R71 for reference are each similar to those of the comparative semiconductor circuit shown in Fig. 6. Output signal V out of the CMOS inverter circuit in the circuit of Fig. 6 is inputted as signal V ga to the gate of NMOS FET M 94 , and input signal V IN1 is inputted to the gate of PMOS FET M 93 . A CMOS inverter is thus constituted from PMOS FET M 93 and NMOS FET M 94 , and output signal V out of the CMOS inverter is outputted as an output of the amplifier circuit. In operation, when input signal V IN1 is at the high level and input signal V IN2i is at the low level, signal V ga presents the high level from the description given above, and consequently, PMOS FET M 93 is OFF while NMOS FET M 94 is ON and output signal V out drops until the ground potential GND is reached. When input signal V IN1 is at the low level and input signal V IN2i is at the high level, signal V ga presents the low level. Consequently, PMOS FET M 93 is ON and NMOS FET M 94 is OFF, and output signal V out rises until it reaches to the power supply potential V CC . When PMOS FET M 93 is OFF, the gate voltage is V G = -0.8 V, and when PMOS FET M 94 is OFF, the gate voltage is V G = 1.0 V, and consequently, little through current flows through the CMOS circuit at the portion. The input DC characteristics of a comparative semiconductor circuit will now be described in comparison with those of a conventional semiconductor circuit. Here, the current mirror type circuit shown in Fig. 2 is employed as the conventional semiconductor circuit while the comparative semiconductor circuit is a circuit in which the circuit shown in Fig. 8 is included by two circuits, one of which receives input signals V IN1 and V IN2i and provides output signal V out and the other of which receives input signals V IN1i and V IN2 having the opposite phase to those of input signals V IN1 and V IN2i , respectively, and provides output signal V outi . Each of the semiconductor circuits is constructed as a sensing amplifier of the differential input type. The semiconductor circuits are designed for high-speed operation, and in the conventional semiconductor circuit, the input voltages are adjusted to level-shifted values and set to signal V INO = V IN2 and signal V INOi = V IN2i so that the responding speed of approximately 0.5 to 1.0 ns may be achieved. Results are shown in Figs. 14A and 14B. Values of output signal potentials V out and V outi with respect to potential difference V IN - V INi of the input signals are shown in Fig. 14A, and values of currents flowing through the circuits with respect to potential difference V IN - V INi of the input signals are shown in Fig. 14B. As seen from Figs. 14A and 14B, with the conventional semiconductor circuit, an input potential difference greater than about 400 mV is required for reversal of the output level, but with the comparative semiconductor circuit, only about 100 to 200 mV is required, and a large through current (about 3 to 5 mA) flows only in a small region. In the conventional semiconductor circuit, since the gate voltage to the PMOS FET is raised, when the PMOS FET is ON, to raise the turning on capacity in order to achieve high speed, when the PMOS FET is to be turned OFF, it is not turned OFF completely and a large through current continues to flow through the PMOS FET. This arises from the fact that, since an NMOS current mirror circuit is involved in the conventional semiconductor circuit, current flows also through the monitoring NMOS of the current mirror circuit on the side on which the output presents the low level, and it can be seen that the conventional semiconductor circuit always dissipates a current of 1 to 1.5 mA. In Fig. 15, values of gains of the semiconductor circuit of the present invention and the conventional semiconductor circuit as amplifiers are seen with respect to input potential difference ΔV IN = V IN - V INi . It can be seen from Fig. 15 that compared with a conventional semiconductor circuit, the semiconductor circuit of the present invention has a high gain which is 5 times at the maximum and 2 times at the average within the range of potential difference ΔV IN = 100 mV. Referring now to Fig. 9, there is shown in circuit diagram a fifth comparative semiconductor circuit. The semiconductor circuit shown is designed so that it can drive a high-output load. The output signal of the comparative circuit shown in Fig. 8 is inputted as signal Vgb to the base of bipolar transistor Q 101 . The emitter of bipolar transistor Q 101 is employed as the output terminal of output signal V out so that it is utilized to pull up output signal V out . Gate signal V ga on the pull-down side is inputted not only to NMOS FET M 94 but also to the gate of NMOS FET M 101 , the drain and the source of which are connected to the collector and the base of bipolar transistor Q 102 , respectively. The collector of bipolar transistor Q 102 is connected to the terminal of output signal V out so that it is utilized to pull down output signal V out . Resistor R 101 is interposed between the base of transistor Q 102 and the ground potential GND to avoid the base of transistor Q 102 being put into a floating state when NMOS FET M 101 is OFF. In short, the fifth comparative semiconductor circuit is a modification to the semiconductor circuit which employs a CMOS inverter for driving output signal V out shown in Fig. 8 in that it additionally includes a BiCMOS inverter for driving output signal V out . Accordingly, the responding speed of the present semiconductor circuit is 0.5 to 1.0 ns, which is substantially equal to that of a circuit of the CMOS driving type, and the present comparative semiconductor circuit can drive a load of 0.5 to several tens pF. Referring now to Fig. 10, there is shown a sixth comparative semiconductor circuit. The semiconductor circuit shown is a sensing amplifier wherein a plurality of BiCMOS type amplifiers are combined into a differential input scheme. Emitter follower circuit EFll generates input signal VIN1, another input signal V IN1i having the opposite phase to that of signal V IN1 and signals V IN2 and V IN2i level shifted from signals V IN1 and V IN1i , respectively. The voltage information is similar to that of emitter follower circuit EF41 shown in each of Figs. 3 and 4. A pair of amplifier circuits are involved including an amplifier circuit which receives input signals V IN1i and V IN2 and outputs output signal V out and another amplifier circuit which receives signals V IN1 and V IN2i and outputs output signal V outi . Each of the amplifier circuits has a simplified circuit configuration wherein a necessary constant voltage portion for reference is connected to the ground potential GND by way of diode D 13 or D 14 . Since the constant voltage may be about 1.0 V as described above, it may be substituted by Vf = 0.8 V by means of a diode. Further, this value is represented in the form of V CC - α from equations (11) and (12) above. In short, while the present value is a value determined from the power supply potential V CC , even if it is set from the ground potential GND, the variation of the gate voltage value by a variation of the potential V CC has little influence upon operation because the variation appears with substantially the same values on both the PMOS FET side and the NMOS FET side. Fig. 16 presents comparative data for cases in which output transistors (an NMOS current mirror circuit) are connected to the output terminals from which signals V out and V outi are outputted and an output load of 30 pF is driven and when a BiCMOS inverter circuit is inserted as a buffer in the conventional circuit shown in Fig. 2 and a similar output load is driven by way of similar output transistors. Referring to Fig. 16, the data is compared in terms of the response time t pd from the input to DC through current at the sensing amplifier portion to output transistor Out. It can be seen that response time t pd is shorter by about 0.5 to 1 ns with the circuit of the present invention, and that the current is decreased by between approximately two thirds to nine tenths. Comparison of the performance in terms of the product of current and response time proves that the circuit of the present invention is reduced to about one tenth the conventional circuit and accordingly, is improved significantly over the conventional circuit. Further, as an application of a semiconductor circuit of the present invention, a logic circuit which operates in accordance with a controlling signal and also serves as an amplifier circuit can be realized without deterioration of the amplification performance. Fig. 11 shows a seventh comparative semiconductor circuit. The present comparative semiconductor circuit is a modification of the comparative semiconductor circuit shown in Fig. 6 in that it additionally includes NMOS FET M 111 , the drain of which is connected to the output terminal of output signal V out of the amplifier circuit of Fig. 6 so that constant voltage V 111 , which is used in the amplifier circuit portion, is also inputted to the gate of NMOS FET M 111 . When voltage V 111 is equal to a preset constant voltage value (up to 1 v), NMOS FET M 111 is OFF, and consequently, the comparative circuit functions as an amplifier circuit. On the other hand, when voltage V 111 is at the high level, both PMOS FET M 71 and NMOS FET M 72 are OFF and NMOS FET M 111 is ON, and consequently, output signal V out presents the low level. In this instance, the comparative circuit has the form in which also a NOR gate is included. In an ordinary logic circuit, since series connection of PMOS FETs or NMOS FETs is required, the characteristics of the amplifier circuit are influenced and a variation in preset gain and/or responding speed cannot be avoided. In the arrangement shown, however, a logic circuit can be incorporated into an amplifier circuit without having a significant influence on characteristics of the amplifier circuit. A eigth comparative semiconductor circuit in which a NOR gate is incorporated similarly is shown in Fig. 12. Referring to Fig. 12, in the semiconductor circuit shown, the base of bipolar transistor Q 121 is connected to an input terminal of voltage signal V 121 , and the emitter of transistor Q 121 is connected to another terminal of output signal V out . When signal V 121 is at the low level (about 1.0 V which is the preset potential), transistor Q 121 is OFF, but when signal V 121 is at the high level, transistor Q 121 is turned ON simultaneously when PMOS FET M 71 and NMOS FET M 72 are turned OFF, and signal V out is consequently put into the high potential condition. The reason why a logic circuit can be constructed readily as described above is that both the PMOS and NMOS FETs which constitute an amplifier circuit can be put into an OFF state by setting the constant voltage for reference to a high voltage approximately equal to the power supply potential V CC . Fig. 13 shows in circuit diagram a ninth comparative semiconductor circuit. Referring to Fig. 13, the comparative semiconductor circuit is formed as a multiplexer which makes use of the characteristics of a semiconductor circuit of the present invention in which PMOS FETs or NMOS FETs can be turned OFF readily and output signal V out can be put into a floating state. The comparative circuit shown in Fig. 6 is employed as amplifier circuit LC131 for a multiplexer. Controlling circuit MS131 for generating constant voltage value V 131 to be inputted to amplifier circuit LC131 is a controlling circuit for the multiplexer. Circuit MS131 receives input signal V 131i at the gates of PMOS FET M 131 and NMOS FET M 132 , the drains of which are both connected and serve as an output terminal for controlling signal V 131 . While the source voltage to PMOS FET M 131 is the power supply voltage V CC , the source voltage of NMOS FET M 132 is inputted to the base of bipolar transistor Q 131 . The emitter of transistor Q 131 is connected to the ground potential GND, and resistor R 131 is interposed between the power source voltage V CC and the output terminal for signal V 131 . Amplifier circuit LC132 and controlling circuit MS132, amplifier circuit LC133 and controlling circuit MS133, ... similar to amplifier circuit LC131 and controlling circuit MS131, respectively, are disposed in parallel to each other, and the output terminals for output signals V out are connected in common. If only one of input signals V 131i , V 132i , V 133i , ... to controlling circuits MS131, MS132, MS133, ... which is to be selected is put into a high-level state, for example, when signal V 131i is put into the high-level state while the remaining signals are all kept in the low-level state, PMOS FET M 131 in controlling circuit MS131 is turned OFF and NMOS FET M 132 is turned ON, and consequently, little current flows through transistor M 131 by way of resistor R 131 and signal V 131i presents the voltage V 131i = V f = 0.8 V. Since amplifier circuit LC131 to which controlling signal V 131 is inputted thus has a sufficiently high value as the constant voltage for reference thereto, it amplifies input signals V IN1 and V IN2 and outputs them to the output terminal for signal V out . In this instance, since all the other constant voltages for reference are equal to the power supply potential V CC , amplifiers LC132, LC133... present a high-impedance state from the output terminals thereof for output signals V out , thereby realizing the function of a multiplexer. As described so far, according to the present invention, when types or switching operation systems of transistors of the pull-up side and the pull-down side of an amplifier circuit at which input signals are to be received are different from each other, the input signals are inputted at individually level-shifted optimum voltages to the transistors. Further, according to the present invention, a high amplifying capacity, high-speed operation, and low current consumption can be realized by applying constant voltages at suitable values for reference. For example, in a circuit in which a CMOS inverter which employs a PMOS FET of the source driving type as a pull-up transistor and an NMOS FET of the gate driving type as a pull-down transistor is employed as a basic circuit, there is a significant effect in improvement such that the amplification gain is two to five times and the response time/current product is one fifth to one tenth that of conventional circuits. Further, according to the present invention, the function of a multiplexer circuit or a logic circuit can be easily provided, and additionally, by making use of a constant-voltage signal for reference for the control of an amplifier circuit, there will be no without deterioration of the amplifying effect of the amplifier circuit. While the invention has been shown and described particularly with reference to preferred embodiments thereof, it will be understood by those skilled in the art that the foregoing and other changes in form and detail may be made without departing from the scope of the invention as defined in the claims.

Claims: A semiconductor circuit for receiving an input signal of a first amplitude and amplifying the input signal (V in ) into an output signal (V out ) of a second amplitude comprising: a first field effect transistor (M42) for receiving a first signal (V in1 ) at the source thereof, a second field effect transistor (M41) for receiving at the gate thereof a second signal (V in2 ), said first and second signals (V in1 , V in2 ) being derived from said input signal (V in ); and an output circuit (M43, M44) electrically connected to said first and second field effect transistor (M42, M41) for outputting said output signal (V out ) in accordance with a difference between the specific conductances of said first and second field effect transistors (M42, M41) which vary in accordance with the first and second signal, comprising a current mirror circuit including a third and a fourth field effect transistor (M43, M44) having opposite conductivity to said second field effect transistor (M41), the drain of said third field effect transistor (M43) for monitoring current being connected to the drain of said second field effect transistor (M41), the drain of said fourth field effect transistor (M44) and the drain of said first field effect transistor (M42) providing said output signal (V out ), whereby said first and fourth field effect transistor (M42, M44) cooperatively form a complementary inverter circuit, characterized by a diode (D 41 ) the anode of which is connected to the source of said first field effect transistor (M42) and receives the first signal (V in1 ); and a current source (I 41 ) being connected between the ground level and both the gate of said second field effect transistor (M41) and the cathode of said diode (D 41 ) outputting said second signal (V in2 ), whereby said second signal (V in2 ) is downward level-shifted by means of said diode (D 41 ). A semiconductor circuit for receiving an input signal of a first amplitude and amplifying the input signal (V in ) into an output signal (V out ) of a second amplitude comprising: a first field effect transistor (M51) for receiving a first signal (V in1 ) at the source thereof, a second field effect transistor (M52) for receiving at the gate thereof a second (V in2 ) signal, said first and second signals (V in1 , V in2 ) being derived from said input signal (V in ); and an output circuit (M53, M54) electrically connected to said first and second field effect transistor (M52, M51) for outputting said output signal (V out ) in accordance with a difference between the specific conductances of said first and second field effect transistors (M52, M51) which vary in accordance with the first and second signal, comprising a current mirror circuit including a third and a fourth field effect transistor (M54; M53) having opposite conductivity to said second field effect transistor (M52), the drain of said fourth field effect transistor (M53) for monitoring current being connected to the drain of said first field effect transistor (M51), the drain of said third field effect transistor (M54) and the drain of said second field effect transistor (M52) providing said output signal (V out ), whereby said second and third field effect transistor (M52, M54) cooperatively form a complementary inverter circuit, characterized by a diode (D 41 ) the anode of which is connected to the source of said first field effect transistor (M51) and receives the first signal (V in1 ); and a current source (I 41 ) being connected between the ground level and both the gate of said second field effect transistor (M52) and the cathode of said diode (D 41 ) outputting said second signal (V in2 ), whereby said second signal (V in2 ) is downward level-shifted by means of said diode (D 41 ). A semiconductor circuit of the ECL input type, wherein the semiconductor circuit as claimed in claim 1 or claim 2 is employed as a level-shifting circuit for amplifying a signal from an ECL input level to approximately the power supply voltage for CMOS or TTL. A semiconductor circuit, wherein the semiconductor circuit as claimed in claim 1 or claim 2 is employed as a sensing amplifier circuit which amplifies a signal from an internal low voltage which is approximately as high as the ECL level to approximately the power supply voltage for the TTL level output. A semiconductor circuit, wherein the semiconductor circuit as claimed in claim 1 or claim 2 is employed as an output buffer circuit for driving an output transistor.

Inventors: TAKAHASHI HIROYUKI, TAKAHASHI, HIROYUKI, TAKAHASHI, HIROYUKI, C/O NEC CORPORATION
Applicants: NIPPON ELECTRIC CO, NEC CORPORATION
Application year: 1992
Main classification: H03K19
IPC codes: G11C11, H03K19