Hello:
I have been tasked with designing a video switch (NTSC) (2 input 1 output for each circuit on each channel) with 8 channels on one board. I chose the OPA 355 with its nice enable pin that should greatly simplify the switching specification. Since I am a digital hardware designer/embedded software developer by trade, I thought I would take baby steps first and design a simple circuit just to ensure I can get video in and video out. I designed a circuit similar to the one on page 11 of the OP355 data sheet. I am using 5vdc instead of 3vdc, The decoupling capacitor I am using is a 220uF, 1210 package, X5R dielectric, 6.3 V surface mount ceramic. I measure about 400mV DC bias at the positive input to the OPA355 so the -0.3V synch pulse should not be in danger of being clipped. the amplifier cicuit has a 1K resistors instead of 640 ohm, and I have a 76 ohm resistor (Digi-key was all out of 75 ohm). My issue is that when I connect the video, the picture is 'brighter' (especially yellow) than the uninterrupted video and the monitor (Vizio 40+in flat screen TV) does not recognize that there is a video input on the screen (a slim band randomly shows up stating 'no video signal'), yet the video is there.. it is just like I said, 'brighter'. The video system is a simple camera that is connected to a DVD recorder. The output of the recorder is connected to the TV monitor. I place my circuit in between the output of the DVD recorder and the TV monitor If I cycle power on the DVD recorder, the video comes back without the 'no video message'. It takes a few seconds for the TV monitor to adjust color and there is a occasional slight jitter in the video. After about 30 seconds, the jitter seems to improve greatly. I feel I am about 95% there, but it has to be 100% because these screens are going to be what customers (Boeing, Raytheon, Lockeheed Martin, US Government) see when they come observe our rocket test firings. Any help woudl be very much appreciated.
Rob
