Cut off adjustment for LNA

Hello,
I am designing an LNA (in Cadence for class project). I am having a simple problem, (sorry for my representation here). I am going Cascode with this one.

I have calculatad values for

, width,

,

, etc.

So far, the cut-off frequency is calculated as

=

; [

=Gate-source cap]

Then, I proceeded to calculate

as:

=

....Eq.(1)

Say, I got 4.25x10^11 for

, and I have a

of .167mA/V2.
Then, the

= 0.17nH,
but due to technical limitation, I need to use

= .21nH.


Now, I need to change the the capacitance by adding something to

so that my

does not change.

Now, the problem is only equation that I find is Eq.(1) which relates to

, but I need to counter the extra

(it changed from .17nH to .21nH) in some way like a equation with

.

The problem is, I cannot find an equation to tackle this.
Any help would be appreciated.

[Just FYI: it is not

. In that case, the increase in "L' would mean a decrease in 'C'.
In my case, the increased

is countered by adding some more capacitance to

]

Thank you for your time!

Finally found a problem in my understanding, (and an equation).

I tried to keep

unchanged. However, it was to change.
In the new (or the proper) approach,
I kept

unchanged.

So, I went like this:

Then,I used

Thank you all!