Clamper (electronics)

Not to be confused with Clipper (electronics), a similar circuit that imposes fixed limits and does not offset the signal.
Not to be confused with Voltage clamp, a technique and device used in electrophysiology.

A clamper (or clamping circuit or clamp) is an electronic circuit that fixes either the positive or the negative peak excursions of a signal to a defined voltage by adding a variable positive or negative DC voltage to it. The clamper does not restrict the peak-to-peak excursion of the signal (clipping); it moves the whole signal up or down so as to place its peaks at the reference level.

A diode clamp (a simple, common type) consists of a diode, which conducts electric current in only one direction and prevents the signal exceeding the reference value; and a capacitor, which provides a DC offset from the stored charge. The capacitor forms a time constant with a resistor load, which determines the range of frequencies over which the clamper will be effective. Although diode clamp is extremely simple and reliable, a critical disadvantage of a diode clamp for many applications is that the forward voltage drop of the diode is highly dependant on temperature, thus making the output voltage of the diode clamp vary with temperature which makes it unsuitable for many applications.

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