Modulating DC Level Relative to Fixed Voltage

Why is that significant? a (different) fixed offset from any of those gets you to the same place. having the sine centered on ground rather than offset from the + or - supply just makes the algebra simpler. the result is the same.

If I understand that'd work.

What are the requirements for thses signals.

Yes, and when going negative it is still negative.

The point of the exercise is to derive both postive and negative referenced sinewaves from one source.

Klaus Jensen

Exactly. But it is done with only one signal suspended midway between the two rails.

Klaus Jensen

That is not what you said.... "derive two signals of differing polarity". The point in the circuit you reference the output to is immaterial. A simple opamp circuit will give you a waveform which can be centered between the two rails. You can then use either rail as your reference or any other point you wish like a virtual ground. The circuit does not change.

What is the significance of referencing the two rails?

Someone asked for the requirements. It would be nice if you gave us the requirements as they were given to you rather than to put them in your own words. I think they are getting mixed up when you frame the requirements according to how you view the problem.

I think Klaus lost his train... >:-} ...Jim Thompson

No. Let's be polite and call it vertical thinking. The train grew wings and exceeded the level of credibility normally enjoyed here.

Klaus Jensen

You can easily get it back on track... just explain, in clear engineering language, _exactly_ what you are trying to do.

Your explanation, so far, has been less than vague. ...Jim Thompson

Agree very confusing. Klaus, why don't you draw a picture of what you want, with all the relevant details. And then post a link. It sounds like an easy job for an opamp or two.

george H.