From: Robert Baer
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Subject: Re: mitigating charge injection in switched capacitor systems...
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Date: Sun, 15 Dec 2002 11:10:05 GMT
NNTP-Posting-Date: Sun, 15 Dec 2002 03:10:05 PST
Organization: EarthLink Inc. -- http://www.EarthLink.net
Jim Thompson wrote:
> On Sat, 14 Dec 2002 09:26:13 GMT,
> Robert Baer ,
> In Newsgroup: sci.electronics.design,
> Article: <3DFAF9BA.CCA9287C@earthlink.net>,
> Entitled: "Re: mitigating charge injection in switched capacitor
> Wrote the following:
> | A "dirty" trick is to use a capacitor (or maybe another fet) driven
> |with an opposite polarity pulse, to cancel the capacitive divider
> It's more than a "dirty trick". Dummy FET's are commonly used in
> monolithic analog switches to accomplish exactly that.
> ...Jim Thompson
> | James E.Thompson, P.E. | mens |
> | Analog Innovations, Inc. | et |
> | Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
> | Phoenix, Arizona Voice:(480)460-2350 | |
> | Jim-T@analog_innovations.com Fax:(480)460-2142 | Brass Rat |
> | http://www.analog-innovations.com | 1962 |
> For proper E-mail replies SWAP "-" and "_"
> I love to cook with wine. Sometimes I even put it in the food.
Yup! Bucket brigade chips do that also.
I call it a "dirty trick" because not everyone thinks of it, and even
using matched FETs does not exactly cancel the effect.
Reasonably decent cancelling is possible, but it seems that exact
canceling, while theoretically possible, in practice it seems
BTW, it is *not* "FET's" because nothing BELONGS to the FET; it is