[sdiy] Temperature Compensated VCO attempt - help?

[Ian Fritz]

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