A differential amplifier circuit includes a first transistor, a second transistor, a field effect transistor (FET) connected between the first transistor and the second transistor, a first current source connected to the first transistor, a second current source connected to the second transistor, and a control circuit. The first transistor and the second transistor generate a differential output signal in accordance with an input signal and a reference signal. The control circuit includes a first resistor and a second resistor connected in series between the drain and the source of the FET, a center node between the first resistor and the second resistor, a third resistor connected between the gate of the FET and the center node, and a variable current source. The variable current source supplies a control current to the third resistor in accordance with a gain control signal. The control circuit controls on-resistance of the FET.