PURPOSE: To prevent an output pulse from outputting in the case of a fine filter output signal and the occurrence of miscount of pulse number by providing a switch and a circuit controlling the switch to the output stage of a comparator.

CONSTITUTION: The output circuit consists of a transmission gate 6 controlling the output of a comparator 4, a P-channel MOS transistor(TR) 7, inverters 8, 12, an integration device 9, a comparator 10 and a reference circuit 11. When the level of a sinusoidal wave signal being the output of a filter 1 is small, the switch 6 provided to the output stage of the comparator 4 inhibits the output of the comparator. Thus, when the output pulse of the comparator is counted by using a microcomputer, the output circuit realizing accurate count is realized.