AC clamp circuit for video applications

This invention is a clamp circuit for a video input. The clamp circuit includes: a coupling capacitor; a differential amplifier comparing a video input to predetermined reference voltage; a clamp transistor having a gate connected to the output terminal of the differential amplifier and a source-drain path connected between a power supply voltage and a second terminal; a resistive element connecting the second terminal of the clamp transistor and the coupling capacitor; a first current sink carrying a first predetermined current from the coupling capacitor to ground; and a second current sink carrying a second predetermined current from the second terminal of the said clamp transistor to ground. The resistive element can be a transistor, a resistor, a diode or a switch.