PURPOSE: To improve both offset accuracy and characteristics of input current by using a feedback circuit of the input current in a current region where the transistor characteristics can be satisfactorily displayed.

CONSTITUTION: An input terminal 15 is connected to the base of the 1st input transistor (TR)11, and at the same time an output terminal 16 and a contstant current source 10 are connected to the emitter of the TR11. A TR12 having the same polarity as the TR11 is cascaded between the TR11 and the constant potential VCC. While TRs 13 and 14 having polarities opposite to the TRs 11 and 12 are cascaded between a constant potential VEE and a VCC 17. The TRs 13 and 14 consist of pnp TRs and can be used in a high current region. In such a constitution, a feedback circuit of input current can be used in a high current region where the TR characteristics can be satisfactorily displayed. Thus, the offset accuracy of the input current is improved.