National AN-299 VCO idea (was: Re: [sdiy] Exponential converter information)

[Ian Fritz]

At 08:48 AM 6/19/05, synth at oldmail.charlielamm.com wrote:
>Nice links....I esp. like this one:
>
>http://www.national.com/an/AN/AN-299.pdf#page=1
>
>Has anyone actually messed around with this? i.e., can you really use a
>LM3046 and the temp dependence of a polystyrene cap as they show here, to
>cancel temp drift of a VCO?

I haven't tried it yet, since I don't really like the heater approach 
(where does the heat go, and what does it do?), but it looks OK.  If the 
poly cap doesn't cancel the linear drift completely, you can take out the 
difference by adding a small dc voltage at the input to the converter 
transistor.  This is explained as part of my general pasivation technique here:
http://home.earthlink.net/~ijfritz/sy_cir7.htm
http://home.earthlink.net/~ijfritz/sy_cir9.htm

  Ian