US 6,982,597 B2
Differential input circuit
Mutsumi Mitarashi, Tokyo (Japan)
Assigned to Oki Electric Industry Co., Ltd., Tokyo (Japan)
Filed on Sep. 12, 2003, as Appl. No. 10/660,771.
Claims priority of application No. 2003-076205 (JP), filed on Mar. 19, 2003.
Prior Publication US 2004/0183597 A1, Sep. 23, 2004
Int. Cl. H03F 3/45 (2006.01)
U.S. Cl. 330—253 19 Claims
OG exemplary drawing
 
1. A differential input circuit, comprising:
a signal input terminal pair for inputting a differential input signal pair which vibrates between a first power supply potential supplied by a first power supply line and a second power supply potential supplied by a second power supply line, wherein the first power supply potential is smaller than the second power supply potential);
a first clamp circuit for generating a first control signal which depends on a higher one of one of said differential input signal pair and a first reference potential, and for generating a second control signal which depends on a lower one of said one of differential input signal pair and a second reference potential;
a second clamp circuit for generating a third control signal which depends on a higher one of the other of said differential input signal pair and said first reference potential, and for generating a fourth control signal which depends on a lower one of the other of said differential input signal pair and said second reference potential;
a first input circuit comprising a first input transistor which inputs said second control signal from a control terminal, where a first main electrode is connected to said first power supply line via a first constant current source, and a second input transistor which inputs said fourth control signal from the control terminal, where the first main electrode is connected to said first power supply line via said first constant current source;
a second input circuit comprising a third input transistor which inputs said first control signal from the control terminal, where the first main electrode is connected to said second power supply line via a second constant current source, and a fourth input transistor which inputs said third control signal from the control terminal, where the first main electrode is connected to said second power supply line via said second constant current source;
an amplification circuit comprising a first output transistor which inputs a third power supply potential (wherein first power supply potential<third power supply potential<the second power supply potential) supplied by a third power supply line and outputs one of the differential output signals from the first main electrode; a second output transistor which inputs said third power supply potential from the control terminal and outputs the other of the differential output signals from the first main electrode; a third constant current source which supplies current received from said second power supply line to the second main electrodes of said first output transistor and said second input transistor; a fourth constant current source which supplies current received from said second power supply line to the second main electrodes of said second output transistor and said first input transistor; a fifth constant current source which emits the current received from the second main electrodes of said fourth input transistor and said first output transistor to said first power supply line; and a sixth constant current source which emits the current received from the second main electrodes of said third input transistor and said second output transistor to said first power supply line; and
a bias circuit for supplying control potential, which makes the voltage between the control electrode and the first main electrode and the voltage between the control electrode and the second main electrode smaller than the potential difference between said first and third power supply potentials, to the transistors constituting said first to sixth constant current sources.