clamping circuit

A clamping circuit is an electronic circuit with which AC voltages are fixed to a reference potential, the clamping voltage.

With capacitive coupling, AC voltages change their average value depending on the positive and negative signal components. This is the case, for example, with unbalanced pulse trains - many zeros, few ones - or with the TV picture, whose mean value shifts to brighter or darker values depending on the brightness component.

Clamping circuits avoid these shifts by clamping a signal component intended for this purpose to the clamping voltage. An example is the analog television signal. So that the brightness level is not affected by the average brightness value of the picture, the black shoulder has been selected as the reference value and is used as the black level reference. During the black shoulder, the coupling capacitance, which has been charged by the changing average value, is briefly charged to the reference potential via a clamping pulse. For pulse trains, the clamping potential can be the pulse ground.

The clamping circuit itself is a simple circuit of diodes, clamping diodes or Zener diodes, which clamps the voltage to the clamping voltage when a given reference level is exceeded.