Phase-sensitive detection circuit is a kind of detection circuit with the ability to distinguish the phase of modulation signal and select frequency.

The function of the shaping circuit in the phase-sensitive detector is to convert the input sine wave into a square wave, so that the electronic switch in the phase-sensitive detector can work normally.

Generally speaking, it refers to using alternating current with peak characteristics to output signals, and then converting them into required DC signals, and outputting intermittent analog signals at a specific time.