[sdiy] Temperature Compensated VCO attempt - help?

[patchell]

    Don't worry Ian...I am measuring the scale at 0,1,2,3 and 4 volts (at the input
to the summing amp)...

Ian Fritz wrote:

> Once again I have to remind you folks that it is totally meaningless to
> give a drift figure unless you also give the corresponding deltaVbe.  At
> deltaBve=0 there is no drift, and drift increases as deltaVbe deviates from
> 0.  The uncompensated case is NOT 3300 ppm/C.  That is simply the
> coefficient of 1/T, before being multiplied by deltaVbe.  It is not the
> drift of the output current.
>
>    Ian
>
> At 01:18 PM 2/1/2003, Magnus Danielson wrote:
> >From: patchell <patchell at silcom.com>
> >Subject: Re: [sdiy] Temperature Compensated VCO attempt - help?
> >Date: Sat, 01 Feb 2003 11:42:33 -0800
> >
> >Jim,
> >
> > > I got enough data now that I could make a calculation, although, before I
> > > will make any claims, I still need more data, but, right now, I came up
> > with
> > > 45ppM/C for the scale drift.  Now, if past experience is any indicator,
> > this
> > > number will jump around a bit as I collect more data, however, this is an
> > > oder of magnitude better (old reading for this same VCO was 400ppM/C) than
> > > any data I have ever collected for a VCO.  I guess if this ends up working
> > > out OK, I'll have to send you some boards Scott.
> >
> >In the neighborhood of 45 ppm/C is much much better than the uncompensated
> >case
> >of 3300 ppm/C. When you are looking at that kind of temperature sensitivites I
> >think the milage can vary depending on what other components are in the VCO.
> >
> >Jörgen reporten on what seemed to be temperature dependence on the LM311
> >comparator in one of his designs. Both resistors and caps can also change
> >depending on which quality was chosen.
> >
> >Anyway, it seems mighty encouraging. The question I'd like to ask, at least
> >retorically, is which stability is needed?
> >
> >Cheers,
> >Magnus

--
 -Jim
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