How can I convert TTL level RGB signals to analogue RGB signals needed by VGA monitor ?
If your TTL level RGB source HSYNC and VSYNC rates compatible with your VGA monitor (or other display device) then you can quite easily adapt TTL level RGB signals to analogue 0.7Vpp signals with few tricks: Circuit 1: simplest adaptation ____ TTL level R, G or B in o——-|____|———-o analogue 0.7Vpp signal out 470 ohm Signal ground o———————–o signal ground This signal will simply convert the signal levels from TTL (0..5V) to the analogue 0.7Vpp signals for 75 ohm loads like normal monitor input. When the circuit put very near to the monitor and the signal source (not long cables) the not perfect impedance does not matter. Circuit 2: impedance matched ____ TTL level R, G or B in o——-|____|—-+—–o analogue 0.6Vpp signal out 330 ohm | | | 100 ohm | | |_| | Signal ground o—————–+—–o signal ground This circuit generates quite perfect impedance matching for 75 ohm load and 75 ohm cable. The downside of this circuit is that this circuit is more com
