SV: Re: [sdiy] Nonlinearities in IR3109 filters

[Sean Costello]

Why so difficult to model diode ladder filters? What about your Moog model,
but with different pole frequencies for each of the 1-pole sections? This
might be an oversimplification, but it would display the key behavior (much
higher feedback gain needed to achieve self-oscillation) in a non-linear
model.

Sean Costello

----- Original Message ----- 
From: "Antti Huovilainen" <ajhuovil at cc.hut.fi>
To: "karl dalen" <dalenkarl at yahoo.se>
Cc: <synth-diy at dropmix.xs4all.nl>
Sent: Wednesday, August 02, 2006 4:07 PM
Subject: Re: SV: Re: [sdiy] Nonlinearities in IR3109 filters


> On Thu, 3 Aug 2006, karl dalen wrote:
>
> > Hmm, what is this smal signal range we are talking about?
> > 20-40mV trough the ladder?
>
> For transistor ladder the level is < 10mV for 1% nonlinearity (of course
> this is affected by feedback so the actual nonlinearity depends heavily on
> cutoff and signal freq content).
>
> > So what hapends above these levels?
>
> All linear methods break down. This includes pole-zero analysis.
>
> I've only looked at modelling diode ladder filter nonlinearities enough to
> say that it'd probably result in a few dozen papers filled with very
> unpleasant equations. Plus I hate the 303 :)
>
> Antti
>
> "No boom today. Boom tomorrow. There's always a boom tomorrow"
>    -- Lt. Cmdr. Ivanova