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[Help] how to calculate characteritic impedendance in cmos

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scuba

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when i draw a line w=30um ,length=100um . what's itimpedence? how to calculate Z0 .if i have known the substrate parameter(TSMC 0.18um).
or which book is relative data.
 

BigBoss

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You may consider like microstrip line on silicon. If we assume the relative permittivity of silicon 11.7 and if we know the substrate height which is generally 100-300um, we can calculate characteristic impedance of this transmission line.

Can't we ??
 

scuba

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Re: [Help] how to calculate characteritic impedendance in cm

i will try it.
i have other question.if i calculate Z0 in cmos as microstrip line. how do i translate loss tangent to conductivity cause i just have conductivity in substrate not loss tangent. what's their relationship. or did you have some example?
thank you.
 

rautio

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Re: [Help] how to calculate characteritic impedendance in cm

Do yourself a favor, download SonnetLite (www.sonnetsoftware.com, I work for Sonnet). Install is a couple minutes. Then do Help->Tutorial and you are up to speed on Sonnet in about an hour. Then capture your line on cmos, including substrate conductivity. Analyze it and you get S-parameters plus characteristic impedance and Eeff. Both Eeff and characteristic impedance are complex for lossy transmission lines.

To determine the accuracy, analyze a second time with half the cell size. The difference is about equal to the error of the smaller cell size result. You should be able to get results to about +/- 0.5% in Zo and +/- 0.1% for Eeff very easily.
 

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