Olin Lathrop wrote on Thursday, February 13, 2003 2:06 PM:

> A switched capacitor filter just switches in/out elements of cascaded
> R/C lowpass filters.

No it doesn't, have a look at a basic electronics textbook and it will
explain what they do and how they work (clue: it's not a set of RC
filters).

>  You only switch it to change the rolloff
> frequency.

No, you apply a signal to control an internal switches, for example have a
look at Horowitz & Hill 2nd Ed, pg 282.

>  It is a passive filter in any one configuration, and does
> not require a clock.

No, it does require a clock, and is usually considered an active filter.

>  You have a chain of resistors in series with
> capacitors to ground thru a FET between them.  Turning on a FET
> enables that R/C filter section.

No, it doesn't.

Sorry Olin, back to electronics 101, as I believe it is called 'over
there'...

:-) :-)

Nigel

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Nigel Orr, Design Engineer                 nigel@axoninstruments.co.uk
Axon Instruments Ltd., Wardes Road,Inverurie,Aberdeenshire,UK,AB51 3TT
               Tel:+44 1467 622332 Fax:+44 1467 625235
                   http://www.axoninstruments.co.uk

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