[sdiy] Tempcos a NoGo

[Ian Fritz]

At 12:29 PM 6/8/2007, Tom Arnold wrote:
>On Fri, Jun 08, 2007 at 08:01:10AM -0600, Ian Fritz wrote:
> > At 09:49 PM 6/7/2007, Tom Arnold wrote:
> > >Sure.  I think its even niftier to encapsulate them on a DIP8 adapter of
> > >course.
> >
> > Aren't you worried about self-heating if you do that?  They're only -- 
> what
> > -- .1 W?
>
>I hadnt noticed a problem.  Its important to note that I use the term
>encapsulation loosly.  I'm using thermal transfer epoxy to bridge from the
>Temco to the transistor pair so its not a large blob covering the whole
>thing.  The outline of the parts is readily visible.

Sounds like you are trying to be careful.  I measured one of these little 
guys to check its tempco and I thought I saw a bit of self heating.  The 
manufacturer warns about this, but doesn't give any guidelines.  The thing 
to look for is pitch drift after a large change in frequency.  I never made 
a VCO using one, so I don't have any characterization of this.  The good 
news is that I measured a tempco of ~3350, essentially perfect for 
transistor compensation.

   Ian