[sdiy] Expo converter tempco placement

[Roman Sowa]

JBT collector current changes x2 when base-emmiter voltage changes by 
about 18mV. This is the law.
And of course collector current is used to charge timing capacitor, so 
time and frequency will also change twice, giving an octave.

Roman

W dniu 2014-07-10 11:35, Justin Owen pisze:
> From: René Schmitz [uzs159 at uni-bonn.de]
>
> Hi René,
>
>> I'd like too add, that if you start to design your scaling summer with a
> 100k input resistance, then using a 1k in the feedback doesn't leave you
> with enough drive for the ~18mV per octave required at the base of the
> expo pair.
>
> (At the risk of embarrassing myself...) Can I ask how (or why...) this '~18mV per octave' is a standard that's quoted so often?
>
> Wouldn't the current output requirement potentially vary depending on the VCO circuit that the current source was driving?
>
> Thanks,
>
> - Justin
>
>
>
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