re need help with video detection circuit verity jack sns com steve verity writes i am trying to build a circuit that detects the presence of video vs a blank screen by monitoring the r g and b outputs of a graphics card it should be able to detect the presence of a single pixel at mhz which would mean detecting a ns pulse it should also be able to tell the difference between a blank screen about mv and a dim screen say around mv oh yes it also needs to be cheap in fact the difference between completely black and completely white is only mv i am wondering if i am going to have to amplify the video signals to make this work try a differential amplifier put back to back diodes between the collectors restrict the voltage swing have ma flow with ohm collector rs and keep the stray c below pf try n s run collector to your logic allen sullivan
