Tempco's

[gstopp at fibermux.com]

     Okay I've located a printout of my post about tempco's (I spooled my 
     archives to hardcopy a while back to save the server's file space). 
     It's a re-print (hand-typed!) from an article in Electronotes #95 page 
     15. I posted it to synth-diy on 5/17/96, and the title was:
     
     "EN Tempco article (very long)".
     
     Like I said it's off the disk now so my only copy is on paper. The 
     answer to Chris's question is yes, you can use either positive or 
     negative tempco resistors, and there's a formula to use for resistors 
     that have a coefficient other than 3300 ppm per degree C. The tempco 
     resides in a voltage divider, and positive or negative coefficient 
     resistors simply get placed on one side or other of the divider. The 
     only restriction is that the coefficient must be 3300 ppm per degree C 
     or higher, not lower (most "normal" resistors are between 20 and 600).
     
     - Gene
     gstopp at fibermux.com


______________________________ Reply Separator _________________________________
Subject: Tempco's
Author:  chrisc at metrics.co.uk at ccrelayout
Date:    2/3/97 8:56 AM


Hi
     If what has been said on the list i scorrect re: the tempco in Gene's 
VCO circuit needing to go *UP* in resistance with increasing temperature 
then those of us in UK definitely *CAN'T* use Farnell PN 143-584.
     I'm investigating the possibilities either of getting a correct 
positive tempco for the 1K part or else replacing the 56K with a negative 
tempco. If we use the 10K equivalent to 143-584, we'd need a normal 180R 
resistor where the 1K was. Will a load of 10180R be too low for the circuit 
that was designed with a load of 57000R in mind?
Answers please..... I've got one of the British tempco catalogues, and I'm 
awaiting another.
We live in hope.....
chrisc