Tempco resistors

[Niklas Lindberg]

On Thu, 11 Dec 1997, Paul Perry wrote:

> At 12:28 AM 11/12/97 -0600, Charlie T wrote:
> >I have discovered a source of tempco resistors, Micro Ohm Corporation, at
> http://www.micro-ohm.com/temperature/temprecflm.html.  The cost per unit is
> almost $20; are these indeed the resistors that circuits such as Gene
> Stopp's AMS1 circuit boards require?  The minimum order is 3 resistors; it
> seems to me I remember somebody posting here that they ordered thirty of the
> components from KRL for $100.  
> 
> ......that looks reasonable since Farnell have 3000ppm/degC 1K for
> $6.59Australian each
> It would be easy to make the required 330ppm 1K by addding a series and
> parallel resistor to this Farnell device....but if anyone is 
> buying a lot of the right one, then I'm happy to buy a dozen or so.
> 

Well, I just wanted to point out (so you don't start barking up
the wrong tree :) that the wanted temperature factor is +3300 ppm/degC
(not 330). So that make the Farnell resistor quite usable (one can
live with the difference of 300 ppm).

You just have to remember that the Farnell tempco has a coefficient
of -3000 ppm/degC, which means that to be able to use it in the
voltage divider of our typical exponential converter (as in ASM-1)
we have to put it in another position and redimension one resistor.
That's exactly what I've done with my ASM-1...

I don't have the schematic in my head, but if you like I could
check it out tonight and get back with a little asciimatic
tomorrow :-)

/ Niklas

<~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~<
 >  Niklas Lindberg                                     >
<   Analogue Synths & Electronics Freak                <
 >                                                      >
<	"The availability of a certain patchcord       <
 >	 is inversely proportional to its need"         >
<                                                      <
 >       _                                Anonymus      >
<_______/ \   _________________________________________<
           \_/