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switch sizing in switched capacitor filters (Read 9491 times)

rajkumar palwai

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Sunnyvale, California

Re: switch sizing in switched capacitor filters
Reply #15 - Oct 29^th, 2011, 2:06am

@ mixed signal,
To reduce the non-linearity due to bulk node , you can do the following.

During the hold phase connect the bulk to ground and during the sampling phase, connect the bulk to input.

So, during the sampling mode ur Vbs=0 and hence u dont see any non-linearity. Also in the hold mode, ur bulk is tied to ground so that no junction diode is forward biased independent of input signal level.

-rajkumar

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rajkumar palwai Community Member Offline Posts: 46 Sunnyvale, California	Re: switch sizing in switched capacitor filters Reply #16 - Oct 29^th, 2011, 2:13am @raja, Yes, part of the circuit uses charge pump to get higher voltages to be able to charge to cap to VDD. Its a standard circuit. I forgot the exact article which gave this architecture.
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loose-electron

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Re: switch sizing in switched capacitor filters
Reply #17 - Oct 29^th, 2011, 12:00pm

mixed_signal wrote on Oct 28^th, 2011, 10:43pm:

Thank you everyone for your valuable replies.

Where should the body of a switch be connected. I m using NMOS switch. should i connect it to ground or the source?

Practically (in real circuits) are the switches in switch capacitor circuits �laid out seperately so that their body can be connected to source to remove body effect. I have heard of deep trench isolation where nmos bulk can be seperated from the substrate.

If i connect body to ground then will the non linearity arising due to body effect cause problem? Simulation seems to be OK.

Thanks

generally body of NMOS is part of substrate.

Jerry Twomey
www.effectiveelectrons.com
Read My Electronic Design Column Here
Contract IC-PCB-System Design - Analog, Mixed Signal, RF & Medical

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