finding lambda of nMOS 0.18u

[bhav]

channel length , lamda, 0.18

how to find lambda(channel length modulation parameter)

from Id vs Vds or Vgs characterstics of an nMOS(0.18u) or pMOS of same technolgy

 

[nxing]

typical lambda cmos 0.18

once you have the describing equation for the transistor's operation, you can sweep vds to solve the equations to find lambda.
Good Luck

 

[evilguy]

lambda in nmos current equation

quote from analysis and design of analog integrated circuits

"The parameter λ is inversely proportional to the effective channel length and a decreasing function of the doping level in the channel. Typical values of λ are in the range 0.05V-1 to 0.005V-1"

"The calculation of λ from device structure is quite difficult because it depend on the variation of Xd with voltage is complicated by the fact that the field distribution in the drain depletion region is not one-dimensional"

some equation that might interest you

Va=ID/(δID/δVDS)
Va=Leff(dXd/dVDS)(-1)
λ=1/Va

If you use BSIM model, you might want to look at CLM parameter in the model. it is described as channel length modulation parameter in BSIM manual. you have to look in BSIM manual on how the model describe the effective channel length modulation using the CLM parameter which i believe the computation is quite complex and not suitable to use for hand calculation.

 

[manish12]

channel length modulation id vds curve

found in any cmos book under section " second order effectes "

 

[sethtalk]

find lambda id vs vds

step1 --> extract Id,Vds data form a given MOS

step2 --> write a code (C,matlab,...) to analysis the data,

ref to book :"CMOS ANALOG CIRCUIT DESIGN",Phillip,E.Allen ,
appendix B,page 750,

Added after 1 minutes:

step1 --> extract Id,Vds data form a given MOS

step2 --> write a code (C,matlab,...) to analysis the data,

ref to book :"CMOS ANALOG CIRCUIT DESIGN",Phillip,E.Allen ,
appendix B,page 750,

 

[mzhanghong]

ads id vds graph

If you are using spectre, a simplest way is the following:
step 1: run a DC operating point simulation.
step 2: print the operating point of the MOSFET concerned.
step3: write down the gds and id from the MOSFET
step4: lamda=gds/id


this results has a little approximation.

 

[bhav]

spectre id vds

i found it this way
take two points on Id vs. Vds curve. this will give two linear equations of Id in terms of Vds (Vgs is same on the curve, so the Vth). so calculated lambda from simple manipulation
Id1 1+lambda*Vds1
--- = -------------------
Id2 1+lambda*Vds2

would any one comment if i have found lambda correctly

 

[vkshenoy]

nmos lambda equation

hey bhav, your method is theoretically correct, and good for previous technologies. but Lambda is not a constant in sub-micron technologies like 0.18um. so you can't determine it using ratios.

mzhanghong's idea is better because it finds the lambda for that particular bias condition.

 

[bhav]

determine lamda of mos

thnks for the comment vkshenoy

 

[microbasly]

how to extract lambda nmos from graph

I previously think that it can be got from the technique file,but it is diappointing,from all views above,i will calculate from the simulation result

 

[aryajur]

how to write code id vs vds graph using matlab

Another method you can try is once you have the family of curves plotted for Id/Vds then simply do the derivative function on the graph, this will give you the gds curve further if you divide this curve by Ids curve you will get the λ curve, and this curve you can keep handy for your design lookup work..

 

[leyla55]

mos id vs vds in matlab

Have a look at this website :

http://www.ph.unito.it/~cobanogl/


and find the Tutorials inteh left hand side by the name of:

Estimating CMOS Hand Calculation Parameters (K, µCox, Vth and lambda)

It says step by step how to calculate the Lambda .