VCO temp compensation

[Martin Czech]

:::I am not complaining about any of the excellent ckts 
:::already existuing, whether on chip heaters, thermistors or whatever.
:::
:::But, it occurs to me that temperature sensing chips are pretty cheap 
:::now and more importantly are available.
:::Couldn't an oscillator be designed where a compensating voltage was
:::derived from the sensor? I'm not talking perfection, just something that
:::most people wd be happy with when gigging.
:::

The problem is your ears. They are quite sensible for frequency, and
even more for beat frequency. This imposes very strict error limits
to wide band osc. For two octaves or so things are easier.  

The linear Korg/Haible/Paia approach is also not so demanding and
quite clever.

If you are going the expo way you simply need a matched pair to convert
first order temp sensitivity into second order: Is saturation current
is eliminated, Ut remains.

If the sensor is not on chip there are problems with sensing time,
the sensor always lags behind the actual temperature. It may work
if the chip/sensor arrangement is very well isolated.

m.c.