[sdiy] Quadrature Trapezoid VCO

[Don Tillman]

   > From: metasonix <metasonix at earthlink.net>
   > Date: Sat, 19 Jul 2003 19:42:20 -0700
   > 
   > Don:
   > >  http://www.till.com/articles/QuadTrapVCO
   > >(Also, I *believe* this is original.  Has anybody seen anything
   > >remotely like it before?) 
   > 
   > There have been thru-zero VCOs--one in the Electronotes
   > collection, which used a similar switching scheme. 

You mean the one that full-wave rectifies the control voltage, drives
a triangle VCO core, and flips the ramping when the control voltage
crosses zero?  

If so, yeah, mine is intended to address the issues of tripping over
zero crossings near 0 Hz.

   > But you've done the first one with quadrature outputs. 

Well, it's not so much quadrature outputs -- the quadrature is
intrinsic to how it works.  At that point the quadrature outputs are
free.

   > (I wouldn't call them exactly sine/cosine, since the waveforms
   > aren't really sines.)

Right, the trapezoid has the same harmonic content as a triangle wave.
So I always refer to the waves as "Trapezoid Sine" ("TSin") and
"Trapezoid Cosine" ("TCos").

   > So--you gonna make a kit or a PC board? Why not?

No, I'm not in that business.  :-)

  -- Don

-- 
Don Tillman
Palo Alto, California
don at till.com
http://www.till.com