[sdiy] Continously Variable Symmetry Triangle

[Don Tillman]

   > Date: Tue, 08 Jul 2003 22:21:53 +0200
   > From: ASSI <Stromeko at compuserve.de>

   > On Tuesday 08 July 2003 09:46, Don Tillman wrote:
   >
   > > So I think you can compensate for this nonlinearity exactly by
   > > preceeding the circuit with an anti-diff-amp (a diff amp in the
   > > feedback loop of an opamp).
   > 
   > Feedback topologies are fun, but I thought it was especially neat
   > that I would not need anything like that.
   > 
   > The loop filter would probably be a bear to design, although it
   > might work at the relatively low frequencies of an LFO (perhaps
   > with a replica oscillator at a scaled up frequency for the PWM
   > generation).  

I don't think it would be a problem at all to put a diff amp (actually
an OTA) in a feedback loop.  You don't need a lot of loop gain because
this isn't a situation where you need wicked good accuracy (do you?).

But this just got me thinking of a better approach... use the CA3280
input diode linearizer; it'll work great here.

  -- Don

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