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This is not a homework question. I need to calculate input impedance for a LNA and this is part of it.

How do you calculate input impedance, Zin, for the circuit below?

I tried by applying an input voltage, V1, and calculate Iin.

Input impedance will be V1/Iin. However, the expression still contains V1 and I can't figure out how to

make it independent on V1.

There is another method that I am not sure.

Input impedance will be equal to the impedance as all independent sources are turned off.

This means that Zin in the picture will be equal to s(Lg + Ls) + 1/(gg + sCgs)

gg is a conductance.

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# Zin of a circuit with independent sources

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