Patent ID: 7667535

Claim:
An amplifier circuit, comprising: an operational amplifier including a pair of differential input terminals; sampling capacitors, connected to the differential input terminals, respectively, which sample input signals; a regulating capacitor, connected in parallel with one end of each of said sampling capacitors, which adjusts a common-mode voltage of differential input voltages to said operational amplifier; and a first switch which short-circuits an output terminal and an input terminal of said operational amplifier, wherein the regulating capacitor includes a gate-channel capacitance of a second switch of which a source terminal and a drain terminal are connected to a path connecting said operational amplifier and said sampling capacitor, the second switch is turned on during an amplifying period of said amplifier circuit and is turned off during a sampling period of said amplifier circuit, and the first switch is turned off during an amplifying period of said amplifier circuit and is turned on during a sampling period of said amplifier circuit.