AW: CA3046 exponential converter

[BJ]

BJ wrote:
> 
> jhaible wrote:
> > I've seen this on some Moog synth (maybe the Rogue), too.
> > You don't really need an extra transistor for temperature sensing, if you
> > monitor the voltage across the transistor of the expo pair with the
> > reference
> > current (the one inside the opamp feedback loop). This works perfectly
> > if you tie its base to GND and use the base of the "output" transistor for
> > the CV input. The only drawback of this method is that you will need a very
> > low impedance resistor divider for the CV in that case (best would be an
> > active divider, i.e. inverting omamp with gain << 1). That's because the
> > accuracy of the exponential function is very sensitive to a resistance in
> > the
> > base of the "output" transistor, while it's not so critical on the
> > reference
> > transistor (which operates at a fixed current anyway).
> >
> > The good thing is that you can really build three tracking expo converters
> > from a single 3046: One reference transistor, 3 output transistors (with
> > individual CV's on their bases), and one heater transistor.
> >
> > One Moog synth (The Rogue or the Micro ?) has a very well tracking VCF
> > built with this method, so it can serve as an additional, tuned VCO.
> >
> > JH.
> 
> Hmm, are you refering to my design around the shemo i sent
> to you OR have you seen this app in a other machines?Where one
> would use the reamining two transistors as an oven as i did.
> If so ,where is it done ,besides the Rouge and the Micro?

The schemo of my proposal for this tripple expoconverter are found at:
http://home8.swipnet.se/~w-88660/schpcb.htm

Any reports regarding to faults or performance upgrading are welcome!

BJ