On Wed, 10 Oct 2001, Olin Lathrop wrote:

> > But then, is there a method to do an A/D on an input
> > signal of 0V to 1V on the 16F873 using Vrefs?
>
> Not if you want full range of the A/D without external parts.  To get the
> full A/D range from a 0 to 1V signal requires an external amplifier.
>
>
  There is a method Olin, without any external operational amplifier.
You need only to sum the input signal with a 2V dc. This is quite simple
if you have an AC input signal. However method depends on the source
impedance of the input signal.
Another tested method is to generate a zero impedance floated point
somewhere at 2V. ( but this one required an OA ) Thus you can measure both
positive and negative signals in an unorthodoxe way. Of course diferential
amplifiers is doing the same thing.

Vasile

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