[sdiy] VCO Linear Voltage

[David G. Dixon]

> >  I think there must be a way to
> >  process the current from 2164 such that it can be fed into any
> >  voltage, but I haven't figured it out yet, and I have a feeling
> >  that it would involve something fairly exotic.
> 
> It only seems exotic until you know what it is called - try "current
> conveyor" in your favourite search engine.  It is also sometimes
> called an "ideal transistor", but that is not the most useful search
> term because different folks have different ideals.

Hmmm.  Very interesting!

I think I may have found another way, but I have to do a bit more thinking
about it to know whether I'm "smokin' crack" or not.  This promising
technique involves putting the output of 2164 through a current-to-voltage
converter with resistor R to make voltage IR, and then feeding this voltage
into a "Deboo integrator" with four equal resistors, also R.  The Deboo
integrator with equal (matched) resistors is a non-inverting integrator with
time constant RC which is indifferent to the voltage on the cap.  This is
because it involves a negative resistor which exactly compensates for the
cap voltage via feedback.  That means that the reset voltage can be switched
between 0 and, say, 5V with no problems, and the 2164 will always see
virtual ground.

Voila! (assuming no crack fumes on this end)