transmission gate sizing

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analog2003

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Hi,

I am unable to decide how to size a transmission gate. I sized them in the ratio of their unCox. The delay is not a huge concern, because the sampling capacitance is very small. Is that it, or some other factor like channel charge injection has to be considered?

Thanks for your help.
 

nsmission gate

analog2003 said:
I am unable to decide how to size a transmission gate. I sized them in the ratio of their unCox.
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In most cases, equal w/l ratios for both p- and nfets are used. But sizing according to their µCox-ratio is also fine, I think.
analog2003 said:
The delay is not a huge concern, because the sampling capacitance is very small.
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Make the w/l as small as possible, just big enough for your max. delay requirement. If 2 or more transmission gates have to match, consider the necessary w*l product for your matching requirement.
analog2003 said:
Is that it, or some other factor like channel charge injection has to be considered?
Click to expand...
Channel charge injection very often is a problem. Consider at least the simplest compensation method with (1/2)*(w/l) anti-phase-switched drain-to-source-shorted compensation fets.
 
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