VCO temp compensation

[Rene Schmitz]

At 10:58 15.07.99 +1000, Paul Perry wrote:
>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.
>
>paul perry melbourne australia 
>
>

Have a look at my vco3, it uses a cheap resistive temperature sensor made
by phillips, the KTY81-120. The price for these is about 0.50 $ here. 
Alternatively check out the second scheme for the LM566 vco, here I've drawn a
NTC compensation scheme. (Though I've not yet tested that schematic as a
whole, I've sucessfully compensated a VCO with the same compensation.)
And lastly I've done a solid state compensation, which can also be found
there.
You have to glue the resistors to the expo transistors in all cases.
This is of course what is done with a Q81 tempco resistor as well, so I
don't get the point of what has been said here. 

Bye
 René

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