Video clamp

摘要

A clamp circuit that reduces low frequency noise on a wideband signal such as a video signal by more than 50 dB is disclosed and includes an input amplifier for obtaining a difference signal that is the algebraic summation between an input signal having periodically spaced synchronization pulses and a reference signal. The reference signal is generated by sampled data techniques and includes a means for removing the synchronization pulses from the signal. After passing the synchronization pulse through a pulse shaper, they are used to operate a sample and hold device which samples the output of the difference amplifier during the synchronization periods and the sampled output, after being passed through a low-pass filter, is used as the reference signal to the difference amplifier which subtracts the reference signal from the wideband signal. An additional amount of low frequency rejection is provided by passing the difference signal through a switching clamp circuit.