Stretching the cable

Differential signalling should bring many benefits to analogue video – less emi, less distortion, lower supply voltage and lower cost – but most applications continue to use single ended 75W coax connections. An impediment to implementing differential analogue video has been the absence of a low cost ic that converts, transmits and receives video over a differential cable. With such parts now available, let’s look at a typical application: sending video over several hundred metres of CAT5 cable. Although a differential circuit looks complex, it’s simply two single ended (SE) circuits configured to produce equal and opposite signals with respect to a common point.