Mumbai University > Electronics Engineering > Sem 4 > Discrete Electronic Circuits

Marks: 4M

A clamper is circuit which is constructed of a diode, resistor and a capacitor that shifts a waveform to certain dc level without changing the appearance of applied signal.

There are two types of clamper circuits:

1. Positive Clamper

2. Negative Clamper

Positive Clamper :

Figure 1 shows the circuit diagram of positive clamper which consist of resistor, capacitor and a diode.

Assume, during first negative half cycle diode D is forward biased which charges capacitor C to Vm with right plate +ve and left plate –ve.

Hence, during positive half cycle diode D is reverse biased. The capacitor does not lose much charge hence voltage across capacitor remains Vm.

Output voltage equation becomes as follows,

Vo= Vi+Vm=Vm+Vm=2Vm

This shows that clamper adds positive dc shift to the input signal. Figure 2 shows the corresponding input and output waveform.

Negative Clamper :

Figure 3 shows the circuit diagram of negative clamper. Negative clamper adds negative dc shift to the input signal.

During positive half cycle diode D is forward biased. Hence, capacitor C starts charging to Vm with left plate +ve and right plate –ve.

Hence, during negative half cycle diode D is reverse biased. The capacitor does not lose much charge hence voltage across capacitor remains Vm.

Output voltage equation becomes as follows,

Vo= Vi-Vm=-Vm-Vm=-2Vm

Figure 4 shows the corresponding input and output waveform.