Ac coupling capacitors in video designs

摘要

Today's integrated video filter/ driver devices can be designed into video systems (set-top boxes, PVRs, TVs) using a wide range of coupling and clamping configurations, such as input ac- or dc-coupling, output ac- or dc-coupling, and various input clamping and bias configurations. With all of these configurations, designers have a number of decisions to make. When the designer decides to ac-couple an input, he or she needs to understand that the dc content of the incoming video signal becomes lost, so the dc bias level will have to be set by the filter/ driver's input bias and clamp circuitry. If the filter input does not have a clamp and bias circuit or an active dc restore loop, then an external bias network will need to be added in order to set the input common-mode level correctly.