tempco power rating

wicked1 · Joined: Apr 24, 2009 Posts: 14 Location: stl

How big do tempco's need to be? I've got several and just noticed they are 1/16 watt!
I ordered them years ago, as people on the SDIY mailing list suggested them. The person who made the post said to order some part number, 1/6 watt.
So, I ordered that. It looks like 1/6 is not a common size and the bag says "1/16 watt". (Im thinking the 1/6 the guy on the mailing list specified could have been a typo, and 1/16 is exactly what I want)

Will those work? I found some other posts where people were talking about using 1/10 watt SMD tempco's, so maybe 1/16 isn't too far off.
I'd obviously epoxy them to the chip they're adjusting.. I'd imagine being so small it wouldn't take much to fluctuate.

My concern w/ them being so small is self heating, or something.
Thanks for any advice.

andrewF · Posted: Mon May 07, 2012 3:58 pm Post subject:

i think in a typical VCO, where approx 18mV/oct is expected at the base of the transistor pair (so say it sees a max of 180mV), a 1k tempco won't have to deal with more than 0.05mW (a lot less).
1/16W rating should be fine.

frijitz · Posted: Mon May 07, 2012 4:07 pm Post subject:

wicked1 · Joined: Apr 24, 2009 Posts: 14 Location: stl

Ok, thanks.. Like Ian said, i'm sure they won't overheat in the sense of a standard resistor failing, but even a little warming would cause the compensation to drift...
Maybe I'll buy a few larger from one of the usual synth vendors, and save these tiny ones for a less critical project. (Im building 3 new vco's and I want them all to be stable and work well together)