The only issue I can see apart from a slight loss of accuracy is that the
acquisition time will have to be be increased.  That may or may not be a big
deal depending on your timing requirements of course.

Mike

> -----Original Message-----
> From: Spehro Pefhany [SMTP:speff@INTERLOG.COM]
> Sent: Thursday, February 21, 2002 2:13 AM
> To:   PICLIST@MITVMA.MIT.EDU
> Subject:      [PIC]: A/D input impedance > 10K
>
> Hi all:-
>
> What would the consequences be of going to 20K on the midrange 10-bit A/D
> input? I've read the reference manual and the data sheet. If the input is
> bypassed with a 0.1uF or something of that ilk, it seems to be primarily
> limited by the worst case leakage current on the input vs. guaranteed
> accuracy. I'm willing to lose 1 bit or 1.5 bits in the A/D, and high
> temperature operation is not required.
>
> Any thoughts on this?
>
> I'd normally put an op-amp in there without much thought, but the
> quantities
> are such that thought will be well rewarded if a few cents can be snipped.
>
> Thanks for any comments & Best regards,
>
> Spehro Pefhany --"it's the network..."            "The Journey is the
> reward"
> speff@interlog.com             Info for manufacturers:
> http://www.trexon.com
> Embedded software/hardware/analog  Info for designers:
> http://www.speff.com
> 9/11 United we Stand
>
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>

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