NF simulation using port as input(cadence spectre)

Hi, there
I am simulating the NF of a differential LNA, and i found the setup confused me much. I use port as my input source,connect in parallel a resistor with this port and assign to this resistor the same resistance value as that of the port resistance(i make this parallel resistor noiseless), under this set up I can get a NF curve. Of course if I drop the resistor in parallel with the port, I got a different curve. surely there is only one true curve. so which setup should I take to get the right value?


B.R.

Julian

Hi, any comment on that? thanks