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Design >> Analog Design >> how to simulate charge injectin?
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Message started by capri on Mar 21^st, 2005, 4:20pm

Title: how to simulate charge injectin?
Post by capri on Mar 21^st, 2005, 4:20pm

I am working on the SC S/H citcuit . Some paper says the simulation of the charge injection effect at the transistor level using SPICE can not yield accurate results, because the incorrect modeling of the MOS's intrinsic charges and the partitioning of the channel charge. Can BSIM3 model be used to simulate this effect accurately? How to decide the charge partition ratio?
thanks

Title: Re: how to simulate charge injectin?
Post by Paul on Mar 22^nd, 2005, 12:05am

Hi Capri,

as you are correctly stating, simulation of charge injection only gives a qualitative feel of what's going on. As the models are not initially derived for transistors operating as a switch, the results are not totally accurate (at least AFAIK).

The proper way to handle this problem is to design a circuit with signal independent charge injection (which leads to an offset only). Even better, signal independent charge injection in a fully differential circuit is 1st order cancelled.

For more information on this solution, have a look at Gregorian-Temes
Analog MOS Integrated Circuits for Signal Processing
by Roubik Gregorian, Gabor C. Temes
and Johns-Martin:
http://www.designers-guide.org/Books/#Johns-1996

Paul