PURPOSE: To reduce power consumption when a reception function is stopped by providing a functional control element at a differential amplifier circuit, and controlling the amplification function of the differential amplifier circuit based on an operation permission signal.

CONSTITUTION: The differential amplifier circuit 11 which performs the differential amplification of two input signals IN1, IN2, and an output control circuit 12 which outputs a differentially amplified signal level based on the operation permission signal IN3 are provided. The functional control element 13 is provided at the circuit 11, and the element 13 controls the amplification function of the amplifier circuit 11 based on the signal IN3. For example, the element 13 consists of an n-field effect transistor TN, and the transistor TN is connected between a differential point (c) provided at the amplifier circuit 11 and a constant current source Io, and the signal IN3 is supplied to the gate of the transistor TN. As a result, it is possible to supply the operation permission signal to the differential input/output stages of the amplifier circuit 11 and to control an amplification output function and to reduce the power consumption when the reception function is stopped.