inherent nonlinearity in mosfet's model BISIM 3 and 4FORId=0

[macg84]

bsim3 vds=0 problem

Hello at all,
I have a question to do ... I read that in BSIM3 and 4 in mosfet's model, when the current circulating in it is zero it creates a discontinuity on the first derivative. Where can I find information about this topic?
Thank you at all

 

[erikl]

Re: inherent nonlinearity in mosfet's model BISIM 3 and 4FOR

Where can I find information about this topic?

You should use the Search function. S. the foll. discussion in this forum:

 

[macg84]

Re: inherent nonlinearity in mosfet's model BISIM 3 and 4FOR

Thank you for the reply and for the very useful manual, then i found the information on my problem, infact I read that in model BSIM 3 and BSIM 4 there is a lack of simmetry in the model, that leads to differnt left and right hand second order derivatives at Vds=0, consequently, the secondo and higher order derivatives do not exist at Vds=0. This situatio is a problem in RF similation if you want mesure IIP3. My new questio is:
How can i do skip thi problem, using the same model BSIM3 adding something in the schematic to delete the non linearity at Vds=0? Can I do this??
I attacched two article on thi topic...
thank you.....

 

[erikl]

Re: inherent nonlinearity in mosfet's models BSIM 3 and 4

I attached two articles on this topic...

Thank you! Very good papers!

How can i skip this problem, using the same model BSIM3 adding something in the schematic to delete the non linearity at Vds=0? Can I do this??

No. The discontinuity at Vds=0 exists inherently in both BSIM models because of their velocity saturation model (s. your Peter Bendix et al. paper). It is not possible to get rid of this inhomogeneity by adding something in the schematic. The only way to avoid it, is to use the SP model - or to stay well away from Vds=0 ;-)

 

[macg84]

Re: inherent nonlinearity in mosfet's model BISIM 3 and 4FOR

not at all, thank you...how can i change the model in cadence? How can i choose the sp model?

 

[erikl]

Re: inherent nonlinearity in mosfet's model BISIM 3 and 4FOR

...how can i change the model in cadence? How can i choose the sp model?

First you must acquire the SP model from Berkeley, and then adapt it to your process tech. Then put it into your PDK path, where the other sim. models reside. After this you must tell your sim. environment where to find it. Normally, this is PDK admin's job! ;-)
Good luck! erikl

 

[macg84]

Re: inherent nonlinearity in mosfet's model BISIM 3 and 4FOR

thank you very much