Patent ID: 7123073

Claim:
An amplifier device for amplifying a differential signal composed of an in-phase signal and an opposite-phase signal, the amplifier device comprising: an amplifier circuit, located on a path from an input terminal of the amplifier device to an output terminal of the amplifier device, for amplifying the differential signal input via the input terminal of the amplifier device, the amplifier circuit having a plurality of adjusting terminals; a feedback circuit, located across an input of the amplifier circuit and an output of the amplifier circuit and including a parallel circuit formed by a resistor and a capacitor connected to each other in parallel, for feeding the output of the amplifier circuit back to the input of the amplifier circuit while changing a phase of the differential signal passing through the feedback circuit; and a phase controller circuit, located between the adjusting terminals of the amplifier circuit and ground, for changing the phase of the differential signal passing through the amplifier circuit, wherein the amplifier circuit includes an in-phase amplifying section having an in-phase adjusting terminal, which is one of the adjusting terminals, and operating based on the in-phase signal of the differential signal, and an opposite-phase amplifying section having an opposite-phase adjusting terminal, which is another one of the adjusting terminals, and operating based on the opposite-phase signal of the differential signal, and the feedback circuit includes an in-phase feedback section that operates based on the in-phase signal and an opposite-phase feedback section that operates based on the opposite-phase signal.