High speed ASM-1 VCO question

[Don Tillman]

   Date: Fri, 02 May 1997 11:36:46 -0700
   From: John Speth <johns at oei.com>

   The goal of the whole circuit (saw osc and extra comparator) is to make a
   CVable duty cycle convertor.

   Does anybody know of a good and simple high freq (100KHz) tri (or
   saw?) osc circuit (and where I can find them)?  Certainly a tri
   wave would mean ringing would be much less of a problem (no fast
   edges except for the peaks). 

The ultra-simple two opamp approach, integrator and schmitt trigger,
works great.  You can find a schematic for this in almost any opamp
application note.  It's better to use a dual comparator circuit for
the schmitt trigger, that's only slightly more complex, and you have
more accurate trip points, which might be important to you.

   From: chordman at flash.net (Synthaholic AKA The Shark)
   Date: Fri, 02 May 1997 18:41:31 GMT

   Your point about the use of a high quality VCO this way is well taken,
   however, what difference would it make whether saw or triangle is
   used?  

It takes extra trouble to make a sawtooth, to make the high speed
resetting work correctly, and ironically the high speed resetting ends
up not making any difference at the output.  Better to have both
slopes contribute equally to the result and have the lowest possible
slope rates.

  -- Don