PURPOSE: To hold the reference level of an input modulated pulse signal constant and to stabilize an output signal by synthesizing an input pulse signal and its negative-phase pulse signal and holding the peak.

CONSTITUTION: The input pulse modulated signal is supplied to a capacitor CH through the 1st operational amplifier OP1 and diodes D1 and D2 to be peak-held. The peak-held value is held until a reset pulse RS is inputted to the base of a transistor TR. The 2nd operational amplifier OP2 performs attenuation by the amount determined by resistances R1 and R2 and the attenuated signal is fed back to an input side negatively. At this time, an out-of-phase composite signal of the input pulses and peak-held component within a time succeeding the input pulses appears at the output of the operational amplifier OP1.