[sdiy] Tempco vs. "Substrate Oven" in VCO and VCF

[Richie Burnett]

> How come I don't see this kind of solution more often? Is the tempco
> solution "better"?

Fairchild's uA726 was a heated differential pair of transistors and was 
common in Roland's analogue synths like the SH series...

http://www.alldatasheet.com/datasheet-pdf/pdf/54850/FAIRCHILD/UA726.html

-Richie,


W dniu 2016-02-29 o 01:33, sleepy_dog at gmx.de pisze:
> Hey there,
>
> first a question about thermistors (this is what "tempco" are, correct?)
> In circuits for voltage control of a VCO or VCF which use a tempco, how
> much could one deviate with the coefficient, say for instance in Thomay
> Henry's newest VCO based on the TLC555 timer? I think it was spec'd at
> 3500 - what if I could get one with 3470 or 3600 more easily?
>
> Also, I find Rick Jansen's Moog VCF schematic interesting, which uses 3
> remaining transistors in a 3046 transistor array as a controlled "oven"
> for the NPN matched pair, to get rid of temperature sensitivity.
> How come I don't see this kind of solution more often? Is the tempco
> solution "better"?
> How much current will the "oven" draw, and does this reduce the lifetime
> of the IC?
>
>
> Regards,
> Steve
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