[sdiy] Operational Transconductance Amplifiers

[stew]

I've used differential amps for distortion for guitar, and recently had the idea of trying the LM13700 but haven't gotten around to it yet. The plan is to make use of both halves of the LM13700 somehow and also make use of the Iabc input, probably driven from an envelope detector. 

Regards,
Stewart.



> Walker Shurlds <walkershurlds at gmail.com> wrote:
> 
> Interesting.  Does anyone use the tanh response intentionally for
> distortion?  The best sounding digital distortion for guitar I've
> encountered was tanh based...
> 
> On Tue, 9 Mar 2010 22:30:09 +0200 (EET)
> Antti Huovilainen <ajhuovil at cc.hut.fi> wrote:
> 
> > On Tue, 9 Mar 2010, Andre Majorel wrote:
> > 
> > > "An OTA is basically a two quadrant multiplier. It multiplies an
> > > input voltage by a control current and produces a current as its
> > > output. The OTA's transfer function is that of a differential
> > > transistor pair, which is pretty convenient, although, a bit tough
> > > to analyze."
> > 
> > Or to put it in very basic maths:
> > Iout = Iabc * tanh(Vin / 2Vt)
> > Vt = ~26mV (kT/q)
> > 
> > No need to bother with gm or unexplained constants.
> > 
> > Antti
> > 
> > "No boom today. Boom tomorrow. There's always a boom tomorrow"
> >    -- Lt. Cmdr. Ivanova
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