PURPOSE: To obtain a current comparison output of high precision even at the time of changing the extent of offset by always equalizing the voltage between the base and the emitter (Vbe) of a first transistor TR and that of a second TR and determining the extent of offset in accordance with a resistance and an operating current source.

CONSTITUTION: When the current flowing to a variable current source 19 is changed for the purpose of changing the extent of offset, not only the voltage drop of a resistance 18 but also voltages Vbe of first and second TRs 14 and 16 are changed. In this case, variations of voltages Vbe of first and second TRs 14 and 16 are equal to each other because of current mirror relations between them, and the voltage of an input terminal 15 is shifted by the variation of the voltage drop of the resistance 18. Thus, the relative comparison precision is not changed from the original state to perform comparison of high precision though the extent of offset is changed.