Patent Abstract:
A receiver circuit includes first and second constant current sources respectively connected to a pair of first and second receiving terminals to receive complementary current signals, a first NMOS transistor connected at a source thereof to the first receiving terminal and the first constant current source and connected at a drain thereof to a first power supply via a first output terminal and first load means, and a second NMOS transistor connected at a source thereof to the second receiving terminal and the second constant current source and connected at a drain thereof to the first power supply via a second output terminal and second load means.

Full Description:
INCORPORATION BY REFERENCE 
   The present application claims priority from Japanese application JP2007-115001 filed on Apr. 25, 2007, the content of which is hereby incorporated by reference into this application. 
   BACKGROUND OF THE INVENTION 
   The present invention relates to a semiconductor device formed as an integrated circuit. In particular, the present invention relates to a technique of a long distance transmission circuit between circuit blocks provided on a semiconductor substrate. 
   On-chip wiring formed on the semiconductor substrate can be represented by a distributed constant line formed of wiring resistance Ru and wiring capacitance Cu as shown in  FIG. 9 . Especially in recent years, the wiring resistance Ru is increased remarkably by finer wiring in the on-chip long distance transmission on the semiconductor substrate. As a result, bluntness of the received waveform caused by the wiring resistance Ru and wiring capacitance Cu becomes large, resulting in a great obstacle to fast transmission. 
   As for schemes for transmitting signals over a long distance transmission line which are not restricted to the top of the semiconductor substrate, two transmitter-receiver circuit schemes are basically known. One of them is the voltage transmission scheme shown in  FIG. 2A  in which voltage signals are transmitted and received in a transmission system having an open receiving end, and it is s scheme used most frequently in transmission on a semiconductor substrate. The other of them is a current transmission scheme shown in  FIG. 2B  in which current signals are transmitted and received in a transmission system having a terminated receiving end. Results obtained by applying the two schemes to long distance transmission using fine wiring on the semiconductor substrate and comparing rise time values of received waveforms are shown in  FIG. 2C . In  FIG. 2C , it is supposed that the wiring pitch is approximately 0.28 μm and the wiring resistance Ru and the wiring capacitance Cu per unit length are 510 Ω/mm and 0.25 pF/mm, respectively. As appreciated from  FIG. 2C  as well, the current transmission scheme is approximately 2.8 times faster than the voltage transmission scheme. The current transmission scheme brings about an effect obtained by making the output impedance of the transmitter circuit and the terminal impedance at the receiving end smaller than the wiring resistance Rt. This effect is brought about by a phenomenon called in general Thomson&#39;s arrival current phenomenon. As for a current transmission scheme for conducting transmission by using wiring formed on a semiconductor substrate, a circuit intended to detect and amplify data stored in a memory cell array in an SRAM and described in “Current-Mode Techniques for High-Speed VLSI circuits with application to Current Sense Amplifier for CMOS SRAM&#39;s,” IEEE JOURNAL OF SOLID-STATE CIRCUITS, VOL. 26, NO. 4, PP. 525-536, April 1991. is widely used. In this circuit, however, a memory cell corresponding to a transmission circuit is driven by a constant current source, and consequently its output impedance becomes much higher than the wiring resistance, the effect of the above-described phenomenon being not obtained. On the other hand, as for a known technique of a conventional transmission circuit capable of utilizing the effect of the above-described phenomenon, JP-A-7-147092 and JP-A-8-162942 can be mentioned. 
     FIG. 7  shows a current transmission circuit formed of bipolar transistors and described in JP-A-7-147092. In this current transmission circuit, Q 3  in a transmitter circuit  101  and Q 5  in the receiver circuit  102  constitute a current switch circuit, and Q 4  in a transmitter circuit  101  and Q 6  in the receiver circuit  102  constitute another current switch circuit. For example, when an input terminal INp in the transmitter circuit  101  is at its high level and an input terminal INn in the transmitter circuit  101  is at its low level, a base potential of Q 3  becomes its high level and a base potential of Q 4  becomes its low level. If the base potential of Q 3  becomes higher than the base potential VB of Q 5 , a current which has flown through a resistor in the transmitter circuit  101  and a constant current source I 2  until then begins to flow through Q 3 . If the base potential of Q 3  becomes higher than the base potential VB of Q 5  by a voltage drop ΔVR caused by wiring  103 , all of the current flows through Q 3 . A relation between Q 4  and Q 6  is opposite to the relation between Q 3  and Q 5 . Therefore, all of a current flowing through a resistor RL 2  and a constant current source I 3  which has flown through Q 4  until then flows through Q 6 . Since Q 5  turns off, an output terminal Op in the receiver circuit  102  goes high. Since Q 6  turns on, an output terminal On goes low. As a result, a voltage signal is output to the output terminals. In this circuit scheme, current signal transmission is implemented by exchanging a current flowing through the resistor RL 1  and the constant current source I 2  or through the resistor RL 2  and the constant current source I 3  between the transmitter circuit and the receiver circuit as a current signal. Since a current is always let flow through Q 3  and Q 4  in the transmitter circuit  101  and Q 5  and Q 6  in the receiver circuit  102 , impedance seen from each of emitters of these transistors becomes very small. As a result, both output impedance of the transmitter circuit and the input impedance of the receiver circuit can be made smaller than the wiring resistance. Therefore, the speed increase effect owing to the Thomson&#39;s arrival current effect is obtained. Even if bipolar transistors in the circuit shown in  FIG. 7  are replaced by NMOS transistors, similar transmission is possible. 
     FIG. 8  shows a current transmission circuit formed of MOS transistors and described in JP-A-8-162942. In this current transmission circuit, a current generated by a constant current source I 1  in the transmitter circuit  101  flows through wiring  103  or  104  according to potentials at input terminals INp and INn. For example, when the input terminal INp in the transmitter circuit  101  is at its high level and the input terminal INn is at its low level, Q 1  turns off and Q 2  turns on, and consequently output terminals Dp and Dn in the transmitter circuit  101  becomes the high level and low level, respectively. Since Q 2  turns on, a current Il of the constant current source I 1  is drawn from an input terminal of the receiver circuit  102  via the wiring  104  at this time. On the other hand, since Q 1  turns off, a current Ih obtained by dividing a potential difference between an input terminal Rp in the receiver circuit  102  and a power supply VDD by a sum of load resistance R 1  and wiring resistance Rt of the wiring  103  flows into the input terminal Rp in the receiver circuit  102 . As a result, a potential difference caused between load means L 3  and L 4  by Il and Ih is output between output terminals On and Op in the receiver circuit  102  as a voltage signal. In this circuit scheme, current signal transmission is implemented by exchanging the current Ih which flows out when the output of the transmitter circuit is at its high level and the current Il of the constant current source I 1  between the transmitter circuit and the receiver circuit as current signals. In this circuit as well, the speed increase effect owing to the Thomson&#39;s arrival current effect can be obtained by setting resistances R 1  and R 2  in the transmitter circuit  101  smaller than the wiring resistance Rt and always letting currents flow through Q 11  and Q 12  and thereby making the input impedance of the receiver circuit lower than the wiring resistance. 
   SUMMARY OF THE INVENTION 
   In the conventional art shown in  FIG. 7 , a current component flowing into the resistor RL 1  in the current signal depends upon the potential at the receiving terminal Rp in the receiver circuit  102 , the wiring resistance Rt of the wiring  103  and the resistor RL 1 . Since the potential at the receiver terminal Rp in the receiver circuit  102  depends upon the base bias voltage VB of Q 5  and Q 6 , therefore, the current signal exchanged between the transmitter circuit and the receiver circuit depends upon the wiring resistance Rt of the wiring  103  and the bias voltage VB. In addition, in the conventional art shown in  FIG. 8  as well, the current signal exchanged between the transmitter circuit and the receiver circuit, i.e., the current Ih which flows out when the output of the transmitter circuit is its high level depends upon the potential at the receiver terminal Rp in the receiver circuit  102 , the wiring resistance Rt of the wiring  103  and the resistance R 1 . Since the potential at the input terminal Rp in the receiver circuit  102  depends upon the gate bias voltage VB of Q 13  and Q 14 , therefore, the current signal in the circuit shown in  FIG. 8  also depends upon the wiring resistance Rt of the wiring  103  and the bias voltage VB. In both conventional circuits, the current signal between the transmitter circuit and the receiver circuit depends upon the wiring resistance and the bias voltage VB as heretofore described. Furthermore, in both conventional circuits, conversion to a voltage signal is conducted by using the voltage drop caused by the current signal and the load resistor in the receiver circuit as described earlier. If the wiring resistance or the bias voltage VB varies, therefore, the current signal varies greatly and consequently the output voltage signal in the receiver circuit varies greatly, resulting in a fear of false operation of the circuit. For suppressing the variation of the current signal, it is necessary to adjust the load resistor in the receiver circuit or the bias voltage VB according to the wiring length. 
   Therefore, an object of the present invention is to provide a transmitter circuit and a receiver circuit of a current transmission scheme, in transmission using wiring between blocks on a semiconductor substrate, capable of suppressing the variation of the current signal caused by variations of the wiring resistance and bias voltage which pose a problem in the conventional circuits and implementing stable signal transmission. 
   Outlines of representative aspects of the present invention which will be disclosed herein will now be described briefly. 
   A receiver circuit included in a transmitter-receiver circuit between circuit blocks of a semiconductor device includes first and second constant current sources respectively connected to a pair of first and second receiving terminals to receive complementary current signals, a first NMOS transistor connected at a source thereof to the first receiving terminal and the first constant current source and connected at a drain thereof to a first power supply via a first output terminal and first load means, and a second NMOS transistor connected at a source thereof to the second receiving terminal and the second constant current source and connected at a drain thereof to the first power supply via a second output terminal and second load means. A gate voltage of the second NMOS transistor is controlled by a voltage signal which is the same in phase with a voltage signal at the first output terminal, and a gate voltage of the first NMOS transistor is controlled by a voltage signal which is the same in phase with a voltage signal at the second output terminal. A current receiver circuit which does not need the bias voltage VB needed in the conventional circuit can be implemented by using the above-described configuration in the receiver circuit. 
   In addition, a transmitter circuit includes a pair of first and second input terminals to receive complementary input voltage signals, a pair of sending terminals to output complementary current signals according to the complementary input voltage signals, a third NMOS transistor connected at a gate thereof to the first input terminal, connected at a source thereof to the first sending terminal, and connected at a drain thereof to a second power supply, and a fourth NMOS transistor connected at a gate thereof to the first input terminal, connected at a source thereof to the second sending terminal, and connected at a drain thereof to the second power supply. 
   In the receiver circuit having the above-described feature, the bias voltage needed in the conventional circuit becomes unnecessary. Unlike the conventional circuit, therefore, variations caused in the current signals between the transmitter circuit and the receiver circuit by variations of the bias voltage VB can be prevented. As a result, variations of voltage signals in the receiver circuit can also be prevented and stable signal transmission becomes possible. In addition, the first NMOS transistor in the receiver circuit and the third NMOS transistor in the transmitter circuit constitute a current switch circuit, and the direction in which the current signals flow through wiring between blocks is changed according to a magnitude relation between gate voltages. Unlike the conventional circuit, the current signals depend upon the current of the first constant current source in the receiver circuit, and the current signals do not depend upon the wiring resistance. A similar operation is conducted in a current switch circuit formed of the second NMOS transistor and the fourth NMOS transistor as well. Therefore, the current signals are not varied by the wiring resistance. Accordingly, variations of the voltage signals in the receiver circuit can also be prevented, and stable signal transmission becomes possible. 
   Other objects, features and advantages of the invention will become apparent from the following description of the embodiments of the invention taken in conjunction with the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a block diagram showing a basic configuration of a transmitter-receiver circuit between circuit blocks according to an embodiment of the present invention included in a plurality of circuit blocks provided on a semiconductor substrate; 
       FIGS. 2A-2C  show results obtained by comparing rise time of a received waveform in voltage transmission with that in current transmission when long distance transmission is conducted by using fine wiring on a semiconductor substrate; 
       FIG. 3  is a block diagram showing a basic configuration of a transmitter-receiver circuit between circuit blocks according to another embodiment of the present invention; 
       FIG. 4  is a block diagram showing a basic configuration of a transmitter-receiver circuit between circuit blocks according to still another embodiment of the present invention; 
       FIG. 5  is a block diagram showing a basic configuration of a transmitter-receiver circuit between circuit blocks according to yet another embodiment of the present invention; 
       FIG. 6  is a block diagram showing a basic configuration of a transmitter-receiver circuit between circuit blocks according to still yet another embodiment of the present invention; 
       FIG. 7  is a configuration diagram of a conventional current transmission circuit formed of bipolar transistors and described in JP-A-7-147092; 
       FIG. 8  is a configuration diagram of a conventional current transmission circuit formed of MOS transistors and described in JP-A-8-162942; and 
       FIG. 9  shows an equivalent circuit of wiring formed on a semiconductor substrate. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Hereafter, embodiments of the present invention will be described in detail with reference to the drawings. Throughout all drawings for describing the embodiments, the same components are denoted by like characters in principle, and their repeated description will be omitted. 
   First Embodiment 
     FIG. 1  shows a circuit configuration of a principal part of a semiconductor device according to a first embodiment. The semiconductor device according to the present embodiment includes a plurality of circuit blocks on the same semiconductor substrate. There is a feature of the present embodiment in a part for transmitting a signal from a transmitter circuit in one of the circuit blocks to a receiver circuit in another one of the circuit blocks.  FIG. 1  shows the feature part. 
   The transmitter/receiver circuit between blocks includes a transmitter circuit  101 , a receiver circuit  102 , and wiring  103  and  104  between blocks. Signal transmission between the transmitter circuit  101  and the receiver circuit  102  is conducted by using current signals. The transmitter circuit  101  includes an NMOS transistor M 1  connected at its gate to an input terminal INp, connected at its drain to a power supply VDD, and connected at its source to ground via a constant current source IP 1 , and an NMOS transistor M 2  connected at its gate to another input terminal INn, connected at its drain to the power supply VDD, and connected at its source to the ground via a constant current source IN 1 . The receiver circuit  102  includes a current receiver block  105  and a level converter block  106 . The current receiver block  105  includes an NMOS transistor M 3  connected at its gate to an output terminal Fn of the level converter block  106 , connected at its drain to the power supply VDD via load means L 1 , and connected at its source to the ground via a constant current source IP 2 , and an NMOS transistor M 4  connected at its gate to an output terminal Fp of the level converter block  106 , connected at its drain to the power supply VDD via load means L 2 , and connected at its source to the ground via a constant current source IN 2 . The output terminal Fn of the level converter block  106  has a potential obtained by applying level shift of Vs to a potential at an output terminal OUTn of the receiver circuit  102  pulled out from the drain of the NMOS transistor M 4 . The output terminal Fp of the level converter block  106  has a potential obtained by applying level shift of Vs to a potential at an output terminal OUTp of the receiver circuit  102  pulled out from the drain of the NMOS transistor M 3 . It is now supposed that voltage amplitude at the input terminals INp and INn and voltage amplitude at the output terminals OUTp and OUTn are Va. The level shift quantity Vs in the level converter block  106  is set so as to satisfy the following condition.
 
Level shift quantity  Vs&gt;ΔVrs−Va  
 
   Here, each of the constant current sources IP 1 , IP 2 , IN 1  and IN 2  has a current value Is. ΔVrs is the product of the wiring resistance Rt of wiring ( 103  or  104 ) between blocks and the current Is of the constant current sources IP 1 , IP 2 , IN 1  and IN 2 . 
   Outline of the operation of the present circuit will now be described. The potential at the power supply VDD is set equal to 1.2 V. As for the input level of the receiver circuit  101 , its high level VIH 1  is set equal to 1.2 V and its low level VOL 1  is set equal to 0.9 V. Total wiring resistance of the wiring  103  and  104  between blocks is denoted by Rt. First, the case where the input terminal INp is at its high level and the input terminal INn is at its low level will now be described. If the potential at the input terminal INp becomes the high level 1.2 V, all of the current of the constant current source IP 2  flows through a route including the NMOS transistor M 1  and the wiring  103 . Since the potential at the gate Fn is lower than a potential obtained by subtracting a voltage drop ΔVRt (=current of IP 2 ×Rt) caused by the wiring resistance Rt and the constant current source IP 2  from the input high level VIH, i.e., 1.2 V, the NMOS transistor M 3  is cut off. As a result, the potential at the output terminal OUTp in the receiver circuit  102  rises up to the potential at the power supply VDD and becomes the high level VOH, i.e., 1.2 V. On the other hand, if the potential at the input terminal INn becomes the low level, i.e., 0.9 V, then the NMOS transistor M 2  is cut off, all of the current of the constant current source IN 1  flows through a route including the NMOS transistor M 4  and the wiring  104 . All of currents of the constant current sources IN 1  and In 2  flows through the NMOS transistor M 4 . As a result, all of the currents of the constant current sources IN 1  and IN 2  flows through the load means L 2 . Therefore, the potential at the output terminal OUTn of the receiver circuit  102  becomes the low level VOL, i.e., 0.9 V. As for the output signal, therefore, its high level is the potential at the power supply VDD whereas its low level depends upon the currents of the constant current sources IP 1 , IP 2 , IN 1  and IN 2  and the load means L 1  and L 2 . Accordingly, the output signal does not depend upon the wiring resistance Rt, and the bias voltage VB is not needed. 
   In the circuit according to the present invention, signal transmission is conducted between the transmitter circuit  101  and the receiver circuit  102  by exchanging the currents of the constant current sources IP 1  and IN 1 , and IP 2  and IN 2  via wiring  103  and  104 , conversion to voltage signals is conducted in the receiver circuit  102 , and the voltage signals are output, as heretofore described. In the circuit according to the present embodiment shown in  FIG. 1 , the current signals do not vary according to the wiring resistance. Therefore, variation of the output voltage signals of the receiver circuit can also be suppressed, and stable signal transmission becomes possible. 
   Second Embodiment 
     FIG. 3  shows a circuit configuration of a principal part of a semiconductor device according to a second embodiment. 
   In this embodiment, the output terminal OUTp pulled out from the drain of the NMOS transistor M 3  is connected to the gate of the NMOS transistor M 4 , and the output terminal OUTn pulled out from the drain of the NMOS transistor M 4  is connected to the gate of the NMOS transistor M 3 . In other words, the configuration in the present embodiment is a configuration obtained by setting the level shift quantity Vs of the level converter block  106  in the receiver circuit  102  shown in  FIG. 1  equal to 0 V. Even if the level shift quantity Vs of the level converter block  106  is 0 V, operation similar to that in the embodiment shown in  FIG. 1  becomes possible provided that the following expression is satisfied:
 
Level shift quantity  Vs&gt;ΔVrs−Va  
 
   In other words, if the input amplitude and output amplitude Va is set greater than the voltage drop ΔVrs caused by the constant current source IP 1 , IP 2 , IN 1  or IN 2  and the wiring resistance Rt of the wiring  103  or  104 , then the high level of the output signal is the potential at the power supply VDD and the low level of the output signal depends upon the current of the constant current source IP 1 , IP 2 , IN 1  or IN 2  and the load means L 1  and L 2 . Therefore, the current signals do not depend upon the wiring resistance, and stable signal transmission becomes possible. 
   Third Embodiment 
     FIG. 4  shows a circuit configuration of a principal part of a semiconductor device according to a third embodiment. 
   In this embodiment, the level converter block  106  in the receiver circuit  102  is formed of an amplifier circuit. In other words, the output terminal OUTp of the receiver circuit  102  is connected to an NMOS transistor M 401  at its gate. The NMOS transistor M 401  is connected at its drain to a power supply VDD 2  via load means R 404  and to the output terminal Fn of the level shift circuit. In the same way, the output terminal OUTn of the receiver circuit  102  is connected to an NMOS transistor M 402  at its gate. The NMOS transistor M 402  is connected at its drain to the power supply VDD 2  via load means R 403  and to the output terminal Fp of the level shift circuit. Sources of the NMOS transistors M 401  and M 402  are connected in common, and a current source Is is connected to the common code. 
   Depending upon the potential relation between the output terminals OUTp and OUTn, the current of the constant current source Is flows through either the load means R 404  or R 403 . As a result, potentials at the output terminals Fn and Fp of the level converter block  106  are determined. For example, if the potential at the output terminal OUTp is high level and the potential at OUTn is low level, then the NMOS transistor M 401  turns on and the NMOS transistor M 402  turns off, and all of the current of the constant current source Is flows through the load means R 404 . Accordingly, the potential at the terminal Fn falls, and the potential at the terminal Fp rises up to the potential at the power supply VDD. Therefore, the signal voltage of the terminals Fn and Fp depends upon the product Va 1  of the current of the constant current source Is and the resistance of the load means R 403  or R 404 . If the output amplitude Va 1  is set greater than the voltage drop ΔVrs caused by the constant current source IP 1 , IP 2 , IN 1  or IN 2  and the wiring resistance Rt of the wiring  103  or  104 , then the high level of the output signal is the potential at the power supply VDD and the low level of the output signal depends upon the current of the constant current source IP 1 , IP 2 , IN 1  or IN 2  and the load means L 1  and L 2 . Therefore, the current signals do not depend upon the wiring resistance, and stable signal transmission becomes possible. 
   Fourth Embodiment 
     FIG. 5  shows a circuit configuration of a principal part of a semiconductor device according to a fourth embodiment. The present embodiment is obtained by removing the constant current sources IP 1  and IN 1  from the transmitter circuit  101  and forming the transmitter circuit in the embodiment shown in  FIG. 1  of the NMOS transistors M 1  and M 2 . The receiver circuit has the same configuration as that of the receiver circuit  102  in the first embodiment shown in  FIG. 1 . 
   In this configuration as well, a route through which the current of the constant current source IP 2  flows depends upon the potential relation between the input terminal INp and the gate Fn of the NMOS transistor M 3  in the receiver circuit  102 . Furthermore, a route through which the current of the constant current source IN 2  flows depends upon the potential relation between the input terminal INn and the gate Fp of the NMOS transistor M 4 . A current flows through either the NMOS transistor M 1  or M 2  in the transmitter circuit  101 , and a current flows through either the NMOS transistor M 3  or M 4  in the receiver circuit  102 . As a result, current signal transmission and conversion of the received current to voltage are conducted. If the potential at the gate Fn of the NMOS transistor M 3  is lower than VIH−ΔVrs when the input terminal INp is at the high level VIH, then the NMOS transistor M 1  turns on and the NMOS transistor M 3  turns off. Therefore, all of the current of the constant current source IP 2  flows through the NMOS transistor M 1 . As a result, the potential at the output terminal OUTp rises up to the potential at the power supply VDD and it becomes the high level. On the other hand, the input terminal INn is at its low level. If the potential at the gate Fp of the NMOS transistor M 4  in the receiver circuit  102  is higher than VIL+ΔVrs, therefore, the NMOS transistor M 2  in the transmitter circuit  101  turns off and the NMOS transistor M 4  in the receiver circuit  102  turns on. Therefore, all of the current of the constant current source IN 2  flows through the NMOS transistor M 4  and the load means L 2 . As a result, a voltage drop equivalent to the product of the current of the constant current source IN 2  and the resistance of the load means L 2  occurs at the output terminal OUTn, and the potential at the output terminal OUTn becomes the low level. Therefore, the voltage signals at the output terminals OUTp and OUTn depend upon the constant current source IP 2  and IN 2  and the load means L 1  and L 2 . Accordingly, the voltage signals do not depend upon the wiring resistance Rt and stable signal transmission becomes possible. 
   Fifth Embodiment 
     FIG. 6  shows a circuit configuration of a principal part of a semiconductor device according to a fifth embodiment. In the present embodiment, the transmitter circuit  101  is formed of constant current sources Is 1 , Is 2  and Idrv, and NMOS transistors M 601  and M 602  which constitute a current switch circuit. The receiver circuit  102  has the same configuration as that of the receiver circuit in the second embodiment shown in  FIG. 3 . 
   Current values of the constant current sources Is 1 , Is 2  and Idrv are set equal to each other. A route through which the current of the constant current source Idrv flows depends upon the potential relation between the input terminals INp and INn. For example, if the potential at the input terminal INp becomes the high level and the potential at the input terminal INn becomes the low level, all of the current of the constant current source Idrv flows through the NMOS transistor M 601 . As a result, the current of the constant current source Is 1  flows into the NMOS transistor M 601 , and the current of the constant current source Is 2  flows from the output terminal Dp into the constant current source IP 2  in the receiver circuit  102  via the wiring  103 . As a result, the NMOS transistor M 3  in the receiver circuit  102  is brought into the cutoff state, and the potential at the output terminal OUTp rises to the potential at the power supply VDD and becomes the high level. On the other hand, since no current flows to the sending end Dn of the transmitter circuit  101 , no current flows through the wiring  104  either. Therefore, all of the current of the constant current source IN 2  in the receiver circuit  102  flows through the NMOS transistor M 4  and the load means L 2 . As a result, the low level is output to the output terminal OUTn because of a voltage drop generated across the load means L 2  by this current. In this embodiment as well, the voltage signals at the output terminals OUTp and OUTn depend upon the constant current source IP 2  and IN 2  and the load means L 1  and L 2 . Therefore, the voltage signals do not depend upon the wiring resistance Rt and stable signal transmission becomes possible. 
   The transmitter and receiver circuit between circuit blocks according to the present invention can be applied to, for example, signal transmission between a plurality of circuit blocks formed on a semiconductor substrate, and in particular to transmission between blocks with a long distance between blocks and large wiring distance. 
   It should be further understood by those skilled in the art that although the foregoing description has been made on embodiments of the invention, the invention is not limited thereto and various changes and modifications may be made without departing from the spirit of the invention and the scope of the appended claims.

Technology Classification (CPC): 7