> -----Original Message-----
> From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] On
Behalf
> Of Michael Watterson
> Sent: 24 May 2010 10:14
> To: Microcontroller discussion list - Public.
> Subject: Re: [EE] relative tolerances of chip resistor arrays
> 
> AK wrote:
> > Hi group.  I'm designing an amplifier that should have a high common
> > mode rejection ratio, and resistor dividers are required on the
> > inputs.  I'm trying to avoid a manual trimming step.  Is there a
> > common error trend of the resistors in a chip resistor array such
that
> > the resistance error between elements is commonly less than the
> > overall resistance tolerance?
> > thanks
> >  -AK
> >
> yes. That's true. Differential error is a lot less than absolute
error.
> It's inherent in manufacturing process.

Not always true, we used a resistor array in a high precision
differential amp circuit some years back because we needed very close
matching over a wide temperature range.  We found the common or garden
resistor arrays used for e.g. terminating busses weren't very good for
this at all.  We sourced a high precision part ($$) in the end that gave
us the required performance.

Mike

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