Capacitorless filters (was:Re: [sdiy] polivoks filter)

[Karl Dalen]

 --- jhaible <jhaible at debitel.net> skrev: > No idea what's inside the
russian parts.
> 
> But the Farfisa Synthorchestra had a 4pole VCF that was built
> without capacitors. It used a quad opamp with
> adjustable internal current sources. And of course there *are*
> capacitors:
> The silicon-made phase compensation that's on chip.

I had that in mind to but quickly realising that having
a production line for 20-25 000 made units relying on 
the phase compensation capacitance wich would in a FET
amp be in the units of pF region i suppose was a bit
hair raising at first thought!

Small capacitors and leakages and temperature shifts
does not sound healty. Well, i dont know much about
silicon process but anyway!

KD
 
> Basically the same structure as an OTA + cap + buffer, only
> scaled down to very small capacitors and very small currents.
> Doesn't work too well at low cuttoff frequencies, no surprise.
> But it's remarkable that it works at all!
>
> JH.
> 
> -----Ursprüngliche Nachricht-----
> Von: Karl Dalen <karldalen at yahoo.se>
> An: <uzs159 at uni-bonn.de>
> Cc: <synth-diy at dropmix.xs4all.nl>
> Gesendet: Samstag, 11. Oktober 2003 01:52
> Betreff: Re: [sdiy] polivoks filter
> 
> 
> > Exactly, listen here to what designer Vladimir Kuzmin
> > says at http://www.muztech.ru/eng/history.php
> >
> > quoute; VCF doesn't have any capacitor at
> >         all and use only two op amps.
> >
> > Now, that's interesting! I wonder how this is done!
> > Another interesting thing is the VCA, it has
> > differential outputs!
> >
> > KD
> >
> >  --- René_Schmitz <uzs159 at uni-bonn.de> skrev: > I wrote:
> > > > The filter caps are not on the filter board, but on the connector
> > > board.
> > >
> > > Oops, no they're not.
> > >
> > > --
> > > uzs159 at uni-bonn.de
> > > http://www.uni-bonn.de/~uzs159
> >
> >
> > Höstrusk och grå moln - köp en resa till solen på Yahoo! Resor på
> adressen
> http://se.docs.yahoo.com/travel/index.html
> >
> 
>  

Höstrusk och grå moln - köp en resa till solen på Yahoo! Resor på adressen http://se.docs.yahoo.com/travel/index.html