Patent ID: 6933783

Claim:
A variable gain differential amplifier comprising: a first transistor having a first terminal receiving a first input signal, a second terminal connected to a first potential through a first load and a third terminal connected to a second potential through a second load; a second transistor having a first terminal receiving a second input signal, a second terminal connected to said first potential through a third load and a third terminal connected to said second potential through a fourth load; and a variable impedance circuit connected between said third terminal of said first transistor and said third terminal of said second transistor, said variable impedance circuit including: a plurality of first variable impedance devices serially connected between said third terminal of said first transistor and said third terminal of said second transistor, and at least one second variable impedance device that is connected between a node between said plurality of first variable impedance devices and said second potential and is turned on/off complementarily to said plurality of first variable impedance devices.