Question

A circuit that clamps the input waveform negatively negative clipper positive clipper negative clamper positive clipper

Answer 1

A negative unbiased clamp is the opposite of the equivalent positive clamp. In the positive cycle of the input AC signal, the diode is forward biased and conducts, charging the capacitor to the peak positive value of VIN. During the negative cycle, the diode is reverse biased and thus does not conduct.