[sdiy] New take on VC moog ladder

[patchell]

    It is posible to get matched JFET pairs.  In the past, I have use the Siliconix
U235 and U401.  However, if you think matched BJT's are expensive, JFET's are even
worse.  You should be able to get either the U401 or U235 from
http://www.future-active.com

Scott Bernardi wrote:

> JFET's are much harder to match than bipolar transistors. (that's why the JFET
> input opamps have looser Vos specs than similar bipolar input opamps). Matching
> discrete JFET's would be darn near impossible (unless you've got a hundred or so
> to work from).  And I'm not aware of any monolithic matched JFET pairs that are
> available (something like the CA3046 but with JFET's).
>
> Stefan Schneider wrote:
>
> > >> what's a problem with the Q13?
> > >
> > >I just thought it was unecessary.
> > >
> >
> > I think it'll be needeed instead... he needs to drive the current up before
> > feeding it back to the ladder. And like they say "You can never have enough
> > buffering" :)
> >
> > >> The output stage at least
> > >> could be buffered? Paul's previous version of this was strange as it
> > >> actually tried to use the Walt Jung design, wasn't it?
> > >
> > >He did cheat some, didn't he? ;O)
> >
> > That kind of cheating is fun :]
> >
> > >In the end, I don't have a hard feeling against it, I just raised a
> > >few opinions on things which I perceived as odd in order to possibly
> > >let Paul see some flukes, if they indeed is there.
> >
> > BTW, I think it'll depend a lot on the matched transistors used on the
> > ladder wether or not Q13 will be necessary... I'm thinking about another
> > cheat on the VC design (Please don't hit me BTW :) Moving into a JFET ladder
> > for extra drive)
> >
> > Cheers
> >
> > Stefan
>
> --
> Scott Bernardi
> sbernardi at attbi.com

--
 -Jim
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