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# Need value for Lambda

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#### suhas_shiv

##### Full Member level 2
I need to calculate R0 for 0.25um TSMC. I am taking a value of 0.1 for lambda. Is it the right value? Thanks

usually lambda is halft of the technology used

if the tech is 0.25 then the lambda will be at 0.125micron...I think the usage of 0.1 micron is quite ok...but not to use the minimum size is a good idea

Lambda is nothing but the twice the channel length.
So 2lambda=.25
lamda=.125

LAMBDA IS NOT THE OPTIMAL SOLUTION.IT IS USED FOR DESIGN REUSE.

Taking values more than .125 is prefferable.

Among .1
.125
.15
I would prefer .15 and more.

Regards
Mahendra

Thanks Guys.
So if I am using the design length as 1um with 0.25um technology, so the lambda is 0.5, right? Appreciate the response.

Yeah that right

suhas_shiv said:
Thanks Guys.
So if I am using the design length as 1um with 0.25um technology, so the lambda is 0.5, right? Appreciate the response.

Wrong!

L=2λ this λ used here is not the lambda you want!

holddreams is right
in same way,
the longer the channel is,the smaller the lambda is.

I'm sorry for my mistake....I misunderstood your 1micron with both 0.25 and 0.5 things...

Ok minimum rule of poly length is 2 λ,. let me elanborate the step..

1. 0.25micron ÷ 2 = 0.125micron

2. minimum length is 0.5micron(2λ, this is where i confuse) but your length is not the minimum...

3.Divide the length with answer in (1)

1micron÷0.125micron = 8

So your lambda for 1u length is 8λ

I applogize for my mistake....

Syukri

The lambda I am talking about here is the channel length modulation parameter. Its units is 1/V. Its inversely proportional to channel length. So what would its value be for 1um length (using 0.25um TSMC technology)?
I think I read somewhere that the value for this lambda is around 0.09-0.1 for 0.25um(when using minimum length). If this value is correct, would it be the same for 1um length using 0.25um technology or would it be slightly different?

Thanks to everyone for helping me out.

suhas_shiv said:
The lambda I am talking about here is the channel length modulation parameter. Its units is 1/V. Its inversely proportional to channel length. So what would its value be for 1um length (using 0.25um TSMC technology)?
I think I read somewhere that the value for this lambda is around 0.09-0.1 for 0.25um(when using minimum length). If this value is correct, would it be the same for 1um length using 0.25um technology or would it be slightly different?

Thanks to everyone for helping me out.

Hi,
In level 1 spice model lambda is hand calculated as follows

LAMBDA = 0.1 / L , where L = ur NMOS/PMOS length in microns.

unit is per volt.

If ur length is 2u then ur LAMBDA is 0.05.

This value is just an approximation for hand calculations.

no it is wrong take value of lambda which is half the gate length in 0.25 CMOS process the gate length is 0.24um

i am not sure about 0.25um but i konw lambda is inversely proportional to channel length.
for 0.18um lambda-n is about 0.77@0.18um

I think there is a confusion here with LAMBDA used in layout design and the Channel length paramater LAMBDA value used in circuit analysis.