PURPOSE: To attain circuit integration while the hysteresis width is set optionally by connecting two diode clamp circuits different in clamp potential to an output terminal of an operational amplifier constituting a comparator circuit to select an upper limit and a lower limit voltage properly.

CONSTITUTION: A potential limit means 3' limiting an output of an operational amplifier 1 within a prescribed range and a comparison signal output means 4' outputting a comparison signal having a hysteresis characteristic in response to the output of the potential limit means are provided. The comparison signal output means 4' uses resistors R6, R7 so as to divide the emitter potential of a transistor (TR) Q5 into a proper value and change the voltage of the comparison signal led out to an output terminal 2 within a range of nearly 0∼Vcc. The hysteresis width VHys of the comparison circuit is expressed as VHys(VH-VL)×R2/R3. In realizing the hysteresis width of 100mV, let VH be 3V and VL be 2V, the resistance ratio R2:R3 is to be selected as 1:10 and the ratio is suppressed to a value giving no hindrance to the IC design.