Hi.

I just simulated optimum noise impedance Zopt = Ropt + jXopt as Vgs changes. And just realise that Zopt changes a lot as Vgs varies. However, this makes me really confused.
According to the simultaneous noise and input power matching procedure below, after steps 2 and 3, Zopt will be fixed.
However, in step 4, until at this time Vgs is chosen. And this will change Zopt.
It seems useless.
Please explain.