Applications of Operational Amplifiers: Clampers

Clampers:

Fig. 3, shows an active positive clamper circuit.

Fig. 3

The first negative half cycle produces a positive OPAMP output, which turns ON the diode. This capacitor charges to the peak of the input with the polarity shown in fig. 3. Just beyond the negative peak the diode turns off, the feedback loop opens, and the virtual ground is lost. Therefore,

v_out = v_in + V_P

Since V_P is being added to a sinusoidal voltage, the final output waveform is shifted positively through V_P volts. The output wave form swing from 0 to 2V_P as shows in fig. 4. Again the reduction of the diode-offset voltage allows clamping with low-level inputs.

During most of the cycle, the OPAMP operates in negative saturation. Right at the negative input peak, the OPAMP produces a sharp positive going pulse that replaces any change lost by the clamping capacitor between negative input peaks.

Fig. 4