# How to find Channel Length Modulation factor Lamda

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##### Junior Member level 2
channel length modulation factor

Best Regards ,

#### dhasmana

##### Member level 5
how to find channel length modulation

Plot the Vds vs. Id characteristic of the device.The slope of the curve (in saturation region) will give the Ron of the device in saturation.Derive the expression for the Ron of the transistor in saturation and equate it to the measured Ron.Substitute for mu, cox etc and u will be able to calculate lambda.

Regards,
Dhasmana.

#### Usman Hai

##### Full Member level 3
lamda length

lamda= 1/(rds . Ids).
So you can plot Ids vs Vds. take the derivative and then inverse you will get waveform of rds. Now multiply it with Ids curve and take the inverse you will get curve something like this

Now you can find the lamda at your desired Vds.
Hope it helps

orz

### orz

Points: 2

#### pixel

channel length modulation, lambda

... and
rds~L/Id

#### Usman Hai

##### Full Member level 3
triode region channel length modulation

yes as λ = 1/Leff (dL/dVds)
dL/dVds = channel length modulation parameter and you can find in model parameters (after doing the DC analysis) as pclm of the specified transistor.

##### Junior Member level 2
channel length modulation factor lambda

Hai ,

Iam Not getting lamda value . By the above values iam getting 10 as lamda .
I want lamda to calculate U and Cox of the device .

Best Regards ,
Mahesh.

#### Usman Hai

##### Full Member level 3
find channel length modulation

You dont need lamda then. Just bias the transistor in deep triode region and find the value of K. In triode there is no channel length modulation so no lambda in triode current equation.
Cox is constant so you can find mobility.
Btw, for 0.18 TSMC process Kn = 350 uA/V and Kp=80 uA/V. These values I get from simulation so may differ slightly from others.

#### kiashee

##### Newbie level 1
find channel length modulation from id

Thank you very much Usman Hai. this is my very first post and i have just found my answer in here... i'l surely love this forum! i am also interested of obtaining lambda and i am using bsim3v3.1 as model...

but i think madhu01 wants to get the U and Cox from the saturation current equation that is why he's looking for the lambda. i also agree also to use the deep triod region equation.

madhu01, if you have the model, you can simply look it in there.. usually it is labeled as Uo. and you can solve cox using permittivity over tox. Tox can also be found at the model's parameters.

#### acbalbason

##### Full Member level 2
hi!

you can simply measure Kp or Kn. you using a spice based software or a cad tool?

- al

#### dragonfury

##### Member level 4
If you are using Cadence Virtuoso software, the value of Gds in the device operating parameters of the transistor can give you the lambda. because Gds = 1/r0 , where r0= 1/ (lambda*Id).

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