[RE: VCO]

[Michael B. Irwin]

About 15 years ago, I built 2 VCO's using CMOS TLC555  timers to use in
a clock circuit for a dual flanger. A CA3046 was used for an expo
current source charging the cap. Reset done with diode and 150 ohm
resistor from timer output. Used a +/- 5 volt supply. Operated up to 1.2
MHz with the cap removed (so the input capacitance of the timer's
trigger and threshold pins was being charged). The bipolar 555 timer
would not reach 1.2 MHz when substituted in the circuit. The  CMOS
TLC555 timer has a very low bias current on it's input pins (several
pA). Both the CMOS and bipolar versions have around 100 ppm timing
stability with respect to temperature. Makes a nice clock for a flanger,
although I have not tried it for generating audio freq sawtooth waves.