About various levels of spice models

Dec 05, 2006 4 Replies
A

Hello,



My question is regarding an ac small signal equivalent circuit and spice models (level3, BSIM etc).


The complete MOS small signal model (i.e. with caps Cgb, Cgs, Cgd, Cbs,



Cbd, current sources gm*vgs, gmb * vbs, and output resistance rds).


Is the above small signal eqvt circuit valid only upto spice level 3 models or will the same small signal equivalent circuit also hold when a BSIM or hspice level 28 model is used?


Do the advanced mos models (BSIM etc) have more compilecated small signal eqvt circuit than the one mentioned above. where can I find it?


Thanks.


-Almitra P.



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J

You need to read your manuals/text books.

...Jim Thompson

| James E.Thompson, P.E. | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC\'s and Discrete Systems | manus | | Phoenix, Arizona Voice:(480)460-2350 | | | E-mail Address at Website Fax:(480)460-2142 | Brass Rat | | http://www.analog-innovations.com | 1962 | I love to cook with wine. Sometimes I even put it in the food.
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A

Hi,

I understand that the more advanced the spice model (BSIM compared to level 1,2,3), more detailed equations are used to obtain a better accuracy. Also lower level models become inaccurate as device sizes shrink.

My question is related to the small signal equivalent circuit.

Whether I use a level 3 model or a BSIM derived model, is it still ok to use the same small signal equivalent circuit.

If you can suggest where can I find the answer that would be useful.

Regards,

-Almitra

Jim Thomps>

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A

Hi,

Some more information about my question.....

The reason that I asked the question is:

Refer to:

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The small signal schematic shown for ac analysis using spice level 1-3 and the schematic shown for higher spice levels is different.

I was not able to understand the extra elements in the BSIM related schematic and hence the question.

Regards, Almitra Pradhan.

snipped-for-privacy@gmail.com wrote:

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J

formatting link

It looks to me that they are modeling the voltage dependant capacitances as complex G sources. (With what seems to be a little help from LaPlace transforms.)

JosephKK Gegen dummheit kampfen die Gotter Selbst, vergebens.   --Schiller
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