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Old 24th Feb 2005, 2:46 pm   #8
oldeurope's Avatar
Join Date: Dec 2003
Location: Solingen, Germany
Posts: 727
Default Re: VHF Modulator wanted

Hi David,
I had a quick view on your schematic.
It is good that you are able to use the SDA/SCL!
This is my great problem for me!

I must look at the data sheet for the IC maybe there is a way to
use the audio section too.

You can use my video stage at the input pin 9 via a cap.
So the 3,5MHz filter problem is solved.

In the audio stage you don't need a tandem pot.
The other problem is the bias adjust via the emitter follower.
It must be temperature compensatet.
You can use a OPamp or a pnp npn emitter follower.

This is the way I would do this:
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