switching caps prob

[Rob Brzykcy]

BTW, if you are switching capacitances in and out of a filter, make sure you
switch them completely out, IOW, dont leave the disabled cap to ground cuz it
will affect you circuit. Switch out BOTH leads of the cap if you want
predictable results. I can't truly explain why, but I tried every configuration
when I was trying to mess with cap values in a filter and I finally ended up
switching both leads out and it worked fine only then.
Rob

Roman Sowa wrote:

> Switched capacitors is a way of replacing a resistor and have the ability
> to change its value.
> A cap grounded at one end has two switches at the other end.
>
> ---/ --*--/ ---
>         |
>       ===
>         |
>
> when 1st one is on, the other is off, and vice versa
> the switches are controlled by clock signal
> the other ends of switches can be seen as resistor terminals.
> Changing clock frequency will change this circuit's resistance
>
> this is widely used in filters, but since clock is often in 50:1 to 200:1
> relation
> to cutoff frequency it's not very usefull at low frequencies.
>
> Roman
>
> > -----Oryginalna wiadomo¶æ-----
> > Od:   Plinio Andres Barraza [SMTP:pab210 at is8.nyu.edu]
> > Wys³ano:      6 listopada 1998 20:17
> > Do:   Paul Perry
> > DW:   synth-diy at mailhost.bpa.nl
> > Temat:        Re: Radio scan controller?
> >
> > I remember a while back a discussion about switched capacitors, someone
> > mentioned they were on the way to being digital.  Are switched capacitors
> > devices that do the equivalent of laying down a series of capacitors of
> > different values and just switching between them?
> >