> >>> Digital@JoesCat.com 7/04/2005 2:36:49 p.m. >>>
> On April 6, 2005 06:23 pm, Paul Gaastra wrote:
> > I am trying to design a dual rail power supply for a photo diode
> > detector.
> 
> Yes I know about the single supply way of doing it but I'm doing this 
> for someone else.  He wants it dual supply to simplify A/D conversion.

I have found several ADCs that accept bipolar inputs (+/- voltages, not
differential) while running from single supplies.  Analog Devices makes
a few, TI does too.  Not sure about others.  For proof, check out the
AD7890.  ISTR it uses input resistors and scaling to keep everything
above ground.  I wouldn't put it past them to do an internal charge-pump
on the sample-and-hold circuitry, either.


What I was looking for when I ran across this chip was a multiple-input
(4 would be good) ADC that did both differential _and_ bipolar inputs.
Any two of these requirements was easy, all three were hard.  Speed,
resolution, etc. not important.  Anyone used such a beast?

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