SV: Re: [sdiy] Wanred (dead or alive) : Pot

[harrybissell]

If you don't mind a ton of distortion, Nyquist says 2X the highest frequency.

That is the highest HARMONIC in the passband, not fundamental.  A saw or
pulse has some VERY high harmonics.

Nyquist limit only gets you an answer of the right POLARITY, you can say for
sure
its positive or negative, but waveshape is totally destroyed.

I'd say you need 10x minimum, and 100x is better.  All your signal path
components
need to do that.  I remember a multiplexed A/D converter with a slow opamp. The
signals were at 60Hz... but the chop frequency was much higher, The opamp could
not
respond.  REALLY threw the software engineer for a loop... as one signal would
seem
to interfere with the adjacent channel, and he was blaming the multiplexer.  :^P

H^) harry

john mahoney wrote:

> > karl dalen wrote:
> > > 4066, 4053,4051, PWM and dead band comparators to set
> > > OFF position! PWM at 100Khz. Gives mix and switch
> > > in many possible ways! Ugh!
>
> Roy J. Tellason wrote:
> > I was wondering a while back whether something of this sort would be
> > workable...
> >
> > Does anybody have any actual circuits that work along these lines?
>
> I've read that the switching frequency must be "much" higher than the
> maximum signal frequency. But, how much is much?
>
> Blacet makes a switched capacitor filter. What's the frequency, John? (Or is
> it proprietary?)
> --
> john <--(highly proprietary)