I have a RGB signal comming from a device that has the voltage level too high for the signals (i think about 2Vpp instead of 750mVpp) and i'm using a voltage divider to drop the voltage to the appropriate levels and then send the signal to an encoder and straight to a RGB table to be used on a RGB monitor (to have RGB encoding to NTSC and direct RGB out at the same time).

I've tried multiple configurations for this, but nothing yet has gave me the results I want (perfect encoding and perfect rgb pass through).

Exactly what configuration do I need to make this work? Something like the first circuit or something like the second circuit? Or something completely different? Where exactly do I need to ac couple the signal? In the places I have the capacitor already?

BTW, the op-amp that im using is the AD8054, which is designed for video signals so I know im using the right kind of opamp for this application.

Attached Images

	circuit2_522.gif (3.4 KB, 118 views)
	circuit1.gif (1.9 KB, 118 views)

 

Did you use the op amp with a dual supply? The Vin hooked up this way will generate negative voltages half the time.

Check that you have met the stability requirements for this high freq op amp. Board layout is important with these frequencies.

Maybe you should also check that the resistors and caps involved are good for high freq. For example, the inductance of the output cap may become significant at high freq.

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I thought what I'd do was I'd pretend I was one of those deaf-mutes.

 

This particular opamp only requires a single 5V supply. Datasheet here: http://www.ortodoxism.ro/datasheets/...s/AD8054AR.pdf

As for the board layout, im using a breadboard for testing but I'm sure it should still work since I can run the signal straight into the encoder or straight into the RGB monitor through the breadboard (with the resistors and caps im using) and will work just fine. The problem I'm having is what configuration I need to use both wit the opamp.