I have a decoder circuit that includes TW9900 video decoder. The decoder doesn't work properly. There is a matching and AC coupling circuit on analog inputs of the decoder. To finding the problem, i scoped the analog signals on PCB. Why i see a negative offset signal at the input of coupling capacitor? Does it normal? Is there any problem that anybody can see?
Yellow one shows input of AC coupling capacitor.
Blue one shows output of AC coupling capacitor.