Zero crossing detecting circuit

摘要

A zero-crossing detecting circuit where the input signal is applied to positive and negative threshold circuits. Each threshold circuit is connected to the input of a respective one-shot circuit which responds to the beginning edge of each output signal from its threshold circuit. The output pulses of both one-shots are applied to a NOR circuit which thereby responds to the beginning edges but not the trailing edges of the signals from the threshold circuits. Accordingly, variations in the trailing edges of the signals from the threshold circuits due to hysteresis or varying propogation times do not effect the circuit's output.