PURPOSE: To eliminate a current due to the effect of drift, by applying a bias power supply to a base of a transistor (TR) of a differential amplifier and feeding back the collector output of another TR to the base.

CONSTITUTION: A bias voltage VB is applied to a base of a differential TRQb from a bias power supply 7 and a collector electrode is connected to a power supply +VCC. An emitter is connected to the emitter of a TRQa and receives the supply of a constant current IO from a constant current circuit P1. The base of the TRQb is connected to an adding input terminal 5 and input signals S1WSm are inputted from input terminals 21W2m'. A load resistor Ro is connected to the collector of the TRQa, and the collector electrode is connected to the base of a negative feedback TRQc. The emitter of the TRQc is provided with an emitter resistor Re, one end of which is connected to the base of the TRQa to form a negative feedback circuit for the TRQa.