PURPOSE: To obtain a hysteresis circuit which makes a hysteresis width constant independently of the polarity of an input signal only by adding one resistance.

CONSTITUTION: A resistance 12a having a resistance value larger than that of a resistance 12 is provided in a position indicated in Fig. This resistance 12a is so adjusted that a DC voltage VINDC between input terminals of a differential amplifier 8 satisfies a formula VINDC=ΔV'R5+VBEOFFSET-ΔVR3>0 if the potential of an inverted input terminal 7 is lower than that of a non-inverted input terminal 6. In this formula, VBEOFFSET is the input offset value of the differential amplifier 8, and ΔVR3 is the voltage drop of a resistance 3, and ΔV'R5 is the voltage drop of a resistance 5. By this constitution, positive feedback due to resistances 5 and 9 is performed to make the hysteresis width constant independently of the polarity of the input signal when the DC voltage VINDC between input terminals of the differential amplifier 8 is higher than zero.