Wave-shaping circuit

摘要

A wave-shaping circuit comprises a dynamic hysteresis generating circuit for generating a dynamic hysteresis voltage having a certain crest value and whose signal level attenuates at a speed proportional to a number of engine revolutions to mask an ignition noise superimposed on an input signal, and a threshold generating circuit for generating a threshold voltage whose signal level increases/decreases in proportion to the number of engine revolutions to mask an interference noise superimposed on the input signal and to reliably detect a minimum level of the input signal. Either the dynamic hysteresis voltage or the threshold voltage, whichever is higher, is selectively output as a comparison reference signal through a high-level selecting circuit.