Clamp (circuit)

A clamp or clamp circuit is an electrical circuit used to limit the excursion of an electrical (usually voltage) signal to a predetermined level.

Operation

It operates by presenting a low impedance to the output signal when the output voltage approaches the preset limit, to prevent the output voltage from exceeding the predetermined voltage level.

The network usually comprises a capacitor, a diode and a resistive element, but it can also employ an independent DC supply to introduce an additional voltage shift. The magnitude of R and C must be chosen so that $t=RC$ is large enough to ensure that the voltage across the capacitor does not discharge significantly during the diode's "Non conducting" interval.

Examples

One common such clamping circuit is the DC restorer circuit in analog television receiver, which returns the voltage of the signal during the back porch of the line blanking period to 0V. Since the back porch is required to be at 0V on transmission, any DC or low frequency hum that has been induced onto the signal can be effectively removed via this method.

External Links

• Electronic Circuits Design For Beginners - Clamp