The clamping circuit essentially consists of an input source, a capacitor of a suitable value and a diode connected in shunt with the output terminals. This clamps the positive peak of the input signal (sinusoidal, in this case) to the zero level. The diode is assumed to be ideal and initially there is no charge on the condenser. vA is the charge built up on the condenser, C. Figure 5.1 shows a basic clamping circuit.
FIGURE 5.1 A negative clamping circuit