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How to extract 're' from an npn model. (Read 96 times)

sazeena

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How to extract 're' from an npn model.
Aug 23^rd, 2006, 9:21pm

It will be great, if any one could tell me how to find (or extract) 're' of an npn model. I have a model of npn, I have to verify that its re behaves correctly or not, by changing either base current or voltage. Also by varying temperature. It does not matter the model is VBIC, hicum or gummel poon or does it ?
I couldnt find much information except in Grey/Meyer's book , 3rd Edition, page.39, saying that 'rex' (I am assuming it 're') which becomes important at high bias currents.

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marekm

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Re: How to extract 're' from an npn model.
Reply #1 - Aug 23^rd, 2006, 9:42pm

It's been a long time, but the way I learned was to forward bias the junctions so that you would basically just have a resistive-tee topology, then just fit s-parameters to get all of them.

Agilent's Franz Sischka has compiled an excellent, practical book, which is available on their web-site:

http://eesof.tm.agilent.com/docs/iccap2002/iccap_mdl_handbook.html

Although it is based on ICCAP, it has a great deal of background on how to do the measurements and the theory behind the extractions (and not just for BJTs). His technique uses the relation Re=dVce/dIb.

Marek Mierzwinski

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