David Minkler wrote:

> Uh, yeah and they need a ratio tempco of 1ppm/(temp range of operation)
> and the opamp needs a better than 1uV input offset and ...
>
> Wouldn't this be easier with a 40-bit ADC glued to a 40-bit DAC by a DSP
> chip to handle the offset and gain calculations ;-)

Well, I don't know about that... you'd have to write the software for the
DSP

If you ask me, which I know you didn't ;) then, since he's spending most of
the gain of the opamp (usually has at least 250000 or 107.96 dB) then what
you have left is pretty darn stable.  Now, that said, the values he's asking
for are unatainable.
0,2V - 0,439026V isn't going to happen.  I'd aim for a range of 0.2V to
0.44V which is a much more likely target.

 As to opamp selection, my suggestion is an opamp with MOSFET inputs, and
rail-to-rail outputs.  Most devices simply don't have the precision to
handle that number of decimal places, but then, I expect that that was
already known.

Good luck.

--Brendan

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