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Simulators >> Circuit Simulators >> How to calculate PS, PD, AS, and AD
https://designers-guide.org/forum/YaBB.pl?num=1223573569

Message started by nobody on Oct 9^th, 2008, 10:32am

Title: How to calculate PS, PD, AS, and AD
Post by nobody on Oct 9^th, 2008, 10:32am

Hello, all

I would like to know how to calculate PS, PD, AS, and AD if width, and length are known. Thanks.
AS / AD area of Source/Drain
PS / PD perimeter of Source/Drain

Title: Re: How to calculate PS, PD, AS, and AD
Post by indysjl on Oct 9^th, 2008, 1:49pm

This will vary based on device architecture, e.g. basic structure vs. folded vs. ring, etc.

If you have the device layout, it should be clear how to calculate areas and perimeters.

If you don't have the layout, and the architecture isn't specified, and you are given W/L, just assume rectangular structure (rectangular gates, sources, drains), and the solution is obvious A=W*L (+Sidewall area if not negligible), P=2W+2L.

Title: Re: How to calculate PS, PD, AS, and AD
Post by Geoffrey_Coram on Oct 20^th, 2008, 12:56pm

AD is not W * L, since W and L are the *gate* dimensions. W is pretty close, but you need the diffusion length. In BSIM4, the model parameters are DMCI and DMCG (Distance from the Middle of the Contact to the Isolation/Gate): AD=AS ~= W * (DMCI + DMCG)

See also this thread: http://www.designers-guide.org/Forum/YaBB.pl?num=1219125207/0#2

Title: Re: How to calculate PS, PD, AS, and AD
Post by indysjl on Dec 17^th, 2008, 10:05am

Good catch. Thanks. A very clear description in the thread.

Are the diffusion length model parameters the same in BSIM3 as BSIM4?

Title: Re: How to calculate PS, PD, AS, and AD
Post by Geoffrey_Coram on Dec 17^th, 2008, 10:20am

indysjl wrote on Dec 17^th, 2008, 10:05am:

Are the diffusion length model parameters the same in BSIM3 as BSIM4?

No. BSIM4 has DMCI and DMCG. I think BSIM3 doesn't have any of this in the original source, but most simulators use the ACM parameter (area calculation method) and HDIF (half the diffusion length).

Title: Re: How to calculate PS, PD, AS, and AD
Post by hzfeiyun on Dec 24^th, 2008, 10:12pm

Geoffrey_Coram wrote on Oct 20^th, 2008, 12:56pm:

agree. please check hspice manual and device layout example from FAB.