[sdiy] ICL8038

[Tavys Ashcroft]

I've been pretty interested in using the ICL8038 as a VCO for 
non-precision stuff.  Right now I'm just getting started with the 
whole synth-making thing, so I'm not too worried about perfection. 
This chip looks really good, though, because I could use all three 
waveforms, have a large frequency sweep range, and adjust duty cycle 
all very easily.

Now I was just on the music machines page and a brief .txt file 
mentioned an electronotes circuit which gives a much larger frequency 
range and is much more useable as a VCO.  Does anyone here know where 
or how I could find such a schematic, or where I would start out to 
design something like this from scratch?

The description was as follows:

In typical Electronotes fashion there follows a "cheater" circuit for
      the 8038 which bypasses the current-to-voltage problem altogether and
      injects exponential current directly into what would normally be pins
      for timing resistors, making the VCO exponential with a 30,000:1
      voltage/frequency sweep. The outputs are Sine, Triangle, Sawtooth,
      Square, and Pulse (with PWM). This circuit uses an NPN matched
      transistor pair, followed by a PNP matched transistor pair, along with
      5 op-amps and a FET.

      While this sounds attractive, if the performance of this VCO is
      expected to be as good as possible, then the two matched transistor
      pairs will add up to about twenty bucks. This combined with the cost
      of the 8038 itself makes this design less attractive than say one of
      the later Electronotes designs which use only one matched pair or even
      a 3046 transistor array, plus a few op-amps, with performance specs as
      good as anything ever available commercially (and better than most).


If passing out electronotes articles is a no-no here (I seem to get 
that drift), then where do I find electronotes articles?  I'm getting 
much more interested in finding such a circuit as my plans-on-paper 
are starting to want to become a real machine, and soon.

-Tavys