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Clamping DC Biased Composite Video Signal Back to ground

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syntax333:
Hi, as the title suggests I want to clamp the DC Biased Composite Video Signal back to its original position.

I have tried to clamp the signal by extracting sync information and drive a switch which connected to ground according to sync info.

The DC bias which I added is approximately 5V. After trying clamp the signal back to ground DC bias drops to 2V. I want the signal at its original position which is 0V.

Are there any suggestions? Thank you.

xavier60:
I have a circuit that will clamp the sync tip to 1V, you want to clamp to 0V?
Can you show us your circuitry?

syntax333:
The circuit I used is shown below. I want to clamp to 0V.

xavier60:
The CSOUT pulses are positive going. They should not be inverted to drive the 4066.
DC restored video signal doesn't tolerate much loading.

EDIT: I was wrong about the CSOUT polarity.

dzseki:
You can use a DC coupled opamp (Au=1 or 2 depending on what output termination you want ), but with DC bias applied to the inverting pin, therefore subtracting that bias from the input signal.

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