volt control of osc triange tilt?

Buck Buchanan voltagecontrolled at home.com
Mon Nov 8 20:12:45 CET 1999


> Looking for a triangle osc, where the tilt of the
> 'triangle' is voltage controlled, from a 'left
> hand' saw thru symmetrical triangle to 'right hand' saw.
> Any ideas?

Hey Paul and all,

I'm working on something like that right now however I must say
immediately my design is intended for use as a LFO and VCAD only - no
precise sweeps of any kind.  I'm calling it a voltage controlled
attack/decay with retrigger option for LFO operation.

So far it's working quite well with an LM13700 in comparator mode as a
voltage controlled current source/sink.  It charges or discharges Ct at
a rate programmed by Iabc with input to 13700 high or low selecting
source or sink operation.  Comparators sence "top" and "bottom" of wave
and trigger a flip flop.  Since Iabc pin on 13700 programs both attack
and decay, a 4066 selects which control voltage path (attack or decay)
the 13700 sees.

I'll admit the circuit's a little convoluted at this point but it seems
to work.  I'm only getting about 6 octaves (linear sweep) of range out
so far but that's probably enough for it's intended purpose.  While very
much a work in progress, if there's anyone who wants to know more I'll
send ya what I got.

See ya,

Buck



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