Osc reset time

[Don Tillman]

Some thoughts on Colin's VCO idea:

Isn't this the way that Exar function generator chip works?  No
matter, I think this approach is new for electronic music work.

It's interesting...  It really is a triangle wave generator, at least
as far as the capacitor is concerned, but it beats out building a
clasic triangle wave generator and waveshaping that to get a sawtooth
because there there no offsets to trim out and therefore no
subharmonic annoyances.

The advantages are nice: you don't require a high current pulse to
discharge the cap and the timing inaccuarcies due to discharge time
are far less.

Note: If you use a 3PDT switch, the switch's on resistance isn't an
issue.  Use separate switches for directing the current source to the
cap and for sampling the cap voltage -- each of those connects to a
very high impedance device so the on resistance doesn't matter.

As Colin pointed out, a simultaneous triangle output would be an
octave below.  It would also have glitches at the peaks.  Better to
run a second current source, cap, and buffer for the triangle --
effectively a second VCO, heavily syncd.

  -- Don