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Modeling >> Semiconductor Devices >> accuracy of PSP and BSIM model in the Accumulation mode
https://designers-guide.org/forum/YaBB.pl?num=1317091940

Message started by aaron_do on Sep 26^th, 2011, 7:52pm

Title: accuracy of PSP and BSIM model in the Accumulation mode
Post by aaron_do on Sep 26^th, 2011, 7:52pm

Hi,

I have a design where one of the transistors is biased with VGS equal to the negative supply voltage (it is an NMOS). I'm wondering whether the transistor model is accurate in this region. I have access to BSIM and PSP models, but they don't agree with each other. My thinking is that the transistor is normally biased with VGS between 0 and VDD, so the modeling accuracy may not be good with VGS << 0.

Any input is appreciated, and links to documents would be helpful too.

thanks,
Aaron

Title: Re: accuracy of PSP and BSIM model in the Accumulation mode
Post by Geoffrey_Coram on Sep 28^th, 2011, 1:42pm

Probably, your characterization department has trouble making good measurements in such a low-current region, or they may not have even looked at data in that region. I would expect it to be more strongly dependent on the accuracy/effort put into the extraction, rather than the model equations (BSIM4 vs PSP), though one might find that the more physical PSP model naturally gives you a consistent and accurate result for low VGS, whereas BSIM4 would need some further empirical parameter adjustments.

Title: Re: accuracy of PSP and BSIM model in the Accumulation mode
Post by aaron_do on Sep 28^th, 2011, 6:14pm

Quote:

Probably, your characterization department has trouble making good measurements in such a low-current region

that sounds right. Thanks.