Introduction:
A clamper is a circuit that is used to shift the DC level of a waveform without changing its shape or altering the frequency content. It consists of a capacitor and a diode, and it can be used to add or remove a DC offset from a signal.

Explanation:
b) Does not change the appearance of the input signal:
A clamper circuit does not change the shape or frequency content of the input signal. It only shifts the DC level of the waveform. The AC component of the input signal remains unchanged.

When an input signal is applied to a clamper circuit, the capacitor charges or discharges through the diode, depending on the polarity of the input signal. This charging or discharging process causes a shift in the DC level of the waveform.

d) Shifts the DC level of the waveform:
The main purpose of a clamper circuit is to shift the DC level of a waveform. This means that the entire waveform is shifted either upwards or downwards by a certain amount. The AC component of the waveform remains unaffected.

The amount of DC shift depends on the charging or discharging time constant of the capacitor. If the capacitor charges slowly, the DC level of the waveform will shift upwards. On the other hand, if the capacitor discharges slowly, the DC level will shift downwards.

Example:
Let's consider an example to understand the operation of a clamper circuit. Suppose we have an input signal with a DC offset of +2V and an amplitude of 2V. When this signal is applied to a clamper circuit with a positive clamper configuration, the diode conducts during the positive half-cycle of the input signal.

During the positive half-cycle, the capacitor charges through the diode, resulting in a shift in the DC level of the waveform. If the charging time constant is chosen appropriately, the DC level can be shifted to a desired value. In this case, the DC level will be shifted to +2V + the charge on the capacitor.

During the negative half-cycle, the diode is reverse biased and does not conduct. Therefore, the capacitor remains charged at the desired level, and the waveform appears shifted.

Conclusion:
In conclusion, a clamper circuit consists of a capacitor and a diode. It does not change the appearance or frequency content of the input signal but only shifts the DC level of the waveform. This makes it useful for adding or removing a DC offset from a signal without altering its shape.