[sdiy] CEM VCF transconductance stage difference!

[karl dalen]

OK, i see, i tought you discussed CEMs!
Anyhow a realizated topology would be interessting to discuss! :-)

Tims page gives a neat hint!

KD

--- Den lör 2008-12-27 skrev Magnus Danielson <magnus at rubidium.dyndns.org>:

> Från: Magnus Danielson <magnus at rubidium.dyndns.org>
> Ämne: Re: [sdiy] CEM VCF transconductance stage difference!
> Till: dalenkarl at yahoo.se
> Kopia: "Scott Nordlund" <gsn10 at hotmail.com>, synth-diy at dropmix.xs4all.nl
> Datum: lördag 27 december 2008 23.59
> karl dalen skrev:
> >> Magnus Danielson
> <magnus at rubidium.dyndns.org>
> >  
> >> You are correct. If all roots have the same real
> position,
> >> they will expand out from that in the shape of a
> circle. The
> >> sign of the feedback will control which
> orientation the
> >> poles will have on the circle. For a 4-pole design
> positive
> >> feedback gives poles at +/- 45 degrees and +/- 135
> degrees
> >> while negative feedback gives poles at 0, +/- 90
> degrees and
> >> 180 degrees. If the poles where not quite on mark
> (they
> >> never are), they will gather first and then expand
> out as
> >> expected but with a slightly skewed position and
> shape.
> > 
> > For wich filter does this apply? OTA, diode or Tr
> ladders?
> > I imagine a well balanced OTA spread their poles
> differently
> > then the diode and Tr?
> 
> It's not dependent on realization topology, it is part
> of the general linear analysis.
> 
> Cheers,
> Magnus


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