Dear Parminder Kaur,

The video and references below could be helpful:

https://www.youtube.com/watch?v=YsosSrWYYBk

https://sudip.ece.ubc.ca/cadence-virtuoso-schematic-simulations/

https://www.google.com/search?sxsrf=AOaemvKAhWWg0qbF0FtYxe-YyHl9kcDrLA%3A1643014618609&lei=2mnuYYbMJM2sqtsP4fK0kAM&q=cmos%20inverter%20problems%20and%20solutions&ved=2ahUKEwiGoc-1gsr1AhVNlmoFHWE5DTIQsKwBKAF6BAhPEAI&biw=1506&bih=738&dpr=2.55

Dear Parminder Kaur,

The auxiliary data below can be of interest:

https://ocw.mit.edu/courses/electrical-engineering-and-computer-science/6-012-microelectronic-devices-and-circuits-fall-2005/projects/cadence_tutorial.pdf

Dear Parminder

it depends on the region of the inverter you operate it. Means, dependent on the operating region of each of both transistor, of PMOS and NMOS (on-off and triode vs. saturation).

But generally gain A=gm/gds, thus take sum of both gm valid for this region and divide it by sum of both gds for this region.

Like

A_inv= (g_mP + g_mN) / (gds_P + gds_N)

Dear Parminder Kaur ,

In order to operate the inverter as an amplifier you have to bias at the intermediate point of the transfer curve of the inverter where Vi=Vo.

The one can measure the gain by applying a small signal at the input and measure the signal output voltage. Av= vo/vi

As you measure the gain of any amplifier where one input a small sinusoidal input and measure its output.

To bias the transistor you need only to connect a high resistance between the input and the output.

Best wishes