Re: How asymmetrical is an op-amp supply allowed to be?

I still don't know what you want. If you want to linearly amplify a small
voltage, you only need to bias a few volts above ground (or below +V as the
case may be), to avoid clipping. If you want to produce a large swing, say
15V peak, you MUST bias it at the half-way point to avoid clipping.

If you specifically *want* clipping, there are better ways than saturating
an op-amp. (When you push an op-amp too far and it smacks into the supply
rail, that's called saturation.)

You keep speaking of offset, but offset is only what you make of it. If
your entire circuit were designed to operate at a bias of say +10V, then
it's an offset in the absolute sense, but for your circuit, something like
9.6V somewhere would be an error offset of 0.4V.

Same thing for ground reference, you might have the entire circuit biased to
0V, but errors could push that up or down a little.

Note that, with respect to the negative rail, this ground-referenced signal
has an absolute offset of as much.

Tim

--
Deep Fryer: a very philosophical monk.
Website: http://webpages.charter.net/dawill/tmoranwms

"Lostgallifreyan" <no-one@xxxxxxxxxxx> wrote in message
news:Xns97B540EF0CBD7lostgallifreyangmail@xxxxxxxxxxxxxxxx
Ok, thanks, I'm convinced. :) That's what I'd hoped, actually.

Would it follow then, that my idea is sound? To have the ground only far
enough above negative to allow through-zero offset correction (and to
bring it in range of the lowest output value) and a positive headroom of
over 30 volts? As the single rail use of a CA3140 can't allow the through-
zero offset correction if the ground is the same as the negative, that
would rule out any advantage of using the CA3140's output swing to
negative
at all, if you solve the problems with the new ground vs the 'real'
negative one. Which in turn allows me to use nice LF412's, which I like a
whole lot better anyway.

Basically, if you see any glaring problems in my scenario, please let me
know. :)


.

Relevant Pages

  • Re: How asymmetrical is an op-amp supply allowed to be?
    ... small voltage, you only need to bias a few volts above ground (or ... below +V as the case may be), to avoid clipping. ... produce a large swing, say 15V peak, you MUST bias it at the half-way ... You keep speaking of offset, but offset is only what you make of it. ...
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