Clamp (circuit)

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A clamp or clamp circuit is an electrical circuit used to prevent another circuit from exceeding a certain predetermined voltage level. It operates by sensing the output voltage of the monitored circuit and then if the output voltage threatens to exceed the preset limit, applies an electric load which draws greater and greater current from the output in a regulated manner in order to prevent the output voltage from exceeding the predetermined voltage level. The clamp circuit works only if it has a lower output impedance than the monitored circuit thereby overpowering that circuit.

The term voltage clamp is often used to refer to the clamp circuit.