I am trying to get the drain transfer function of a MOSFET by setting the drain to source voltage as the input and the gate to source voltage as the output. I created the following circuit in LTSpice:
When I run an AC simulation, the Bode plot shows no change in the gain with an increase in the frequency.
However, when I change the gate to the input and the drain-source as the output, I get the waveform that I am expecting.
Does anyone know why this is happening? Is the circuit even set up in the right way to get the transfer function of the drain?
Edit 1: The circuit I am trying to model is below. I am trying to find the transfer function where Vd is the input and Vg is the output.