[sdiy] VCO Drift

[Ian Fritz]

Tim --

The cap gives a "tuning" drift (as opposed to a "scale-factor" drift), and 
is easily compensated with a trimmer plus a resistor.  See R13 and R14 here:

http://home.earthlink.net/~ijfritz/sy_cir9.htm

   Ian



At 12:17 PM 7/29/2006, Tim Ressel wrote:
>Yo,
>
>Had a thought. I'm using the heater servo method on my
>VCOs to keep the expo convertor in line. That means
>the polyprop cap is probably the next biggest in terms
>of tempco. I wonder if the heater servo trick would
>work for it as well?
>
>Something like: wrap a 1-watt resistor to the cap with
>(what else?) Kapton tape, add a diode (or transistor
>in diode mode), and entomb in styrofoam. Servo the
>whole thing for temperature with the same curcuit as
>the expo. Keep it at 60C or so.
>
>I figure the rest of the VCO is just resistors, and
>those can be gotten in tempcos down to 10ppm without
>breaking a sweat.
>
>So like, how nutz is this idea??
>
>--Tim (nailing jello to a tree) Ressel