[sdiy] tempco resistors

[David G. Dixon]

Speaking of tempcos, this reminds me of something that I have been meaning
to ask on the list for a while.

There was a discussion recently about non-tempco circuits for temperature
compensation of expo converters.  I believe that Jim Patchell and Ian Fritz
have built such circuits, and perhaps others have as well.

I notice in Horowitz and Hill in the "Circuit Ideas" section of the opamp
chapter that there is a circuit for a "temperature-compensated log
converter."  It looks like two complete log amps, with one used for
compensation of the other.  Has anyone tried to use this circuit, or even
analyzed it to see how it works?  It looks a fair bit simpler than what was
discussed before.

David G. Dixon
Professor
Department of Materials Engineering
University of British Columbia
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Canada
 
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> -----Original Message-----
> From: Neil Johnson [mailto:neil.johnson97 at ntlworld.com]
> Sent: Thursday, January 22, 2009 3:51 PM
> To: David G. Dixon
> Cc: 'peter edwards'; 'sdiy'
> Subject: Re: [sdiy] tempco resistors
> 
> David,
> 
> The Farnell part number is 1174306.  Looking this up it is a TYCO
> ELECTRONICS - LT300014T261K0J temp.co resistor with 3000ppm/'C
> slope.  Here's the Tyco product page:
> 
> http://catalog.tycoelectronics.com/TE/bin/TE.Connect?
> C=1&M=BYPN&TCPN=1624329-2&RQPN=LT300014T261K0J
> 
> which has a link to the PDF spec page.
> 
> Not quite the 3900ppm/'C that is usually used, but a lot better than
> nothing!
> 
> Cheers,
> Neil
> --
> http://www.njohnson.co.uk
>