Frame synchronisation signal clamping cct. - clamps bottom to fixed reference value using capacitor and diode

摘要

The clamping circuit has a capacitor in the signal path and a diode controlled by a clamping potential and switched by a voltage comparator controlled by the synchronisation pulses and the clamping potential. The voltage comparator consists of a differential amplifier whose non-inverting input is connected to the signal path behind the capacitor, inverting input to the clamping potential and output to the diode. So soon as the input voltage of the differential amplifier (A), arising from the difference between the potentials of the video signal and the clamping (U), becomes positive a voltage of e.g. 3V. appears at the output. The latter is zero when the input potential is negative.