MUX

[Harry Bissell]

Gotta jump in here...
the best caps for S/H are Polystyrene. Polyester (Mylar) has some dielectric
absorption.
This allows some charge to be "lost" into the dielectric... only to reappear
mysteriously
during the hold interval... Temp stability is worse for Mylar, but for S/H
its not a problem.
Ceramics (invalues large enough for S/H) are usually not Temperature stable
either. Save these for decoupling and other non critical apps.

If people want I could past the "Capacitor Primer" again... I thought it was
lost but found a copy at work.

Mikko Helin wrote:

> On Fri, 3 Dec 1999, Guido Goebertus wrote:
>
> >
> > Can I use standard CMOS 4051/4067 for the MUX? Or is it better to use
> > HCT series? What would be a good choice for the hold caps (type,value)?
>
> Use the CMOS muxes as you can use them with >5 V voltages, and
> the max. CV out is about 10 V - Vref for 127 MIDI notes in 1/2 steps
> is 127/12 = 10.583333... V, so 12V is a good Vcc for the mux.
>
> Use 0.1 uF caps with TL082 or TL084 op amps. I think polyester
> caps are OK in S/H's, though there might be better ones, but
> ceramic caps are not recommended (though I don't know why).
>
> I think at PAiA site (www.paia.com) has schematics of the
> MIDI2VC8 converter, see how the S/H's are done there.
>
> -Mikko
>
> >
> > Guido
> > --
> >
> >         \|/
> >        (o o)
> > --oOOO---OOOo--------------/|\-Falcon----------
> >
> > L  |||||||||||||||||||||||||||||||||||||||||||||
> > db -50  -40 -30  -24   -18   -12    -6    0 over
> > R  |||||||||||||||||||||||||||||||||||||||||||||
> >
> > ------Guido Goebertus THD Studio Amsterdam------
> > ---------->Total Harmonic Distortion<-----------
> >
> >