How to caculate by hand using BSIM3v3 Model parameter

[jimmyshu]

bsim3v3 model parameters

Hello everyone! I am a beginner of analog IC design, and I have some questions about how to use BSIM3v3 model parameters to design by hand. From BSIM3v3 model parameter UO, VTHO, TOX can be found, and COX can be get by COX=εOX/TOX, but lambda is unknown. Someone has said that it can be extracted by ploting curve Ids-Vds, but I found lambda extracted from curve Ids-Vds was variable in different VGS and W/L value, so I'm not sure which lambda value I can use in formula for caculating by hand. For example, If I want to design a OP, gain can be get by Av=gm*ro. Because of ro=1/lambda*Ids, I can't get Av and many others by hand without lambda.
I need your help. Thank you![/quote]

 

[Blackuni]

bsim cox

Hi jimmyshu,

do operating point analysis this will print the value of gds from this you can find lamda and early voltage This is what i do but its a approximate and involves spice tool.

Hope this helps! let me know if u want complete flow

Thanks

 

[jimmyshu]

bsim3v3 model parameters cox

Is this the way of caculating?
get gds and id from operating point analysis, and lamda=gds/id?
but i found the value of lamda is still large variable for different vgs and w/l. maybe it's true that lamda is useless for BSIM3v3. So do you have better method to caculate Av(0) and ro by hand?
thanks so much!

 

[evilguy]

description of bsim3v3 model

if lambda that you mention stand for chanel length modulation. you can obtain it straight from bsim3 parameter if i'm not mistaken the paramter is PCLM. please consult BSIM3 manual to verify that couse i'm not really sure myself.

-evilguy-

 

[walker5678]

bsim3v3 users manual

Lambda is much dependent on the channel length, bigger L has smaller lambda and so has higher ro

 

[jimmyshu]

lambda + bsim model

I've found methods in Allen's book to exact parameters such as Lambda, K', gamma for hand caculation from Ids-Vds curves. Does anyone use this way to get parameters for first step design?
Hello, evilguy, I have a question that whether PCLM in BSIM3v3 can be used to substitute lambda for hand caculation.
Thanks!

 

[evilguy]

bsim3v3 gds

Hello, evilguy, I have a question that whether PCLM in BSIM3v3 can be used to substitute lambda for hand caculation.
Thanks!

I'm not really sure about it. It just states PCLM is channel length modulation in BSIM3.3 manual. i think you should browse through the manual and see when this PCLM parameter is used in the model equation. sorry not really help you much regarding this.

 

[walker5678]

spice pclm parameter

I think we can not use PCLM as lambda directly, since different channel length transistor has different lambda, but the PCLM is unique. So i think there must be some adjustment factor in the model equations to calculate lambda.

 

[jimmyshu]

ro from model

walker5678, I agree with your point. I think the way of geting lambda is to run a single MOS Ids-Vds simulation sweeping different L value, and get different lambda for each L value.

 

[abhaykochhar2]

cox bsim3v3

hii.. i would like to ask one question..
how we can use readymade models like BSIM, MOS (Philips), etc models in VHDL-AMS tool of synopys???
waiting for ur replies...