How to simulate gm for input rail-to-rail amplifier?

[fuxinmingming]

Hi guys,

How should I simulate the gm of the input rail-to-rail stage(since gm is dependent with the biasing of the opamp)? Thanks

Regards

 

[steinar96]

Since transconductance is defined as ratio of change in output current to change in input voltage you should be able to aquire this from a simulation by applying 2 different voltages to the state and write down the resulting currents. After that you can just take the ratio of the difference between the currents to the ratio of the difference in the voltages you applied.

 

[dick_freebird]

I would look at the extrema and center. Or step through
it more finely, even. Depending on whether you are looking
for spec-compliance or deeper/finer understanding.

 

[htetlinnaung]

I also need to know how to simulate to get gm vs Vcm in Cadence IC virtuoso. Please help me and advice me .