How to simulate the result of rail-to-rail input Op

[porschesun]

I do know how to simulate the gm of a transistor by using deriv function. However, I wanna run the result of gmp+gmn vs Vicm. I can't use the above method because the current will be flat when the vicm reaches transition point.
It turns out that the gm will be zero when the slope of current is going to zero.

Does anyone help me solve this problem and run the right graph of this circuit.
Thank you,

Jason

 

[erikl]

It turns out that the gm will be zero when the slope of current is going to zero.

I think this is correct, as one input pair always gets inactive at the resp. border of the ICM.

As \[gm = \frac{\partial Id}{\partial Vgs} \] and \[ \partial Id \] --> 0 , gm also will trend to zero.

 

[porschesun]

Hey Erikl:

But I wanna see the characteristic of gm of the rail-to-rail op. It might be
gm=gmp when vicm< Vdsat+Vgsn
gm=gmn when vicm>Vdsat+Vgnp
gm=gmp+gmn when Vdsat+Vgsn>vicm>Vdsat+Vgnp

I am supposed to see the graph of this trend based on the book of Allen Holberg.

 

[erikl]

I wanna see the characteristic of gm of the rail-to-rail op. It might be
gm=gmp when vicm< Vdsat+Vgsn
gm=gmn when vicm>Vdsat+Vgnp
gm=gmp+gmn when Vdsat+Vgsn>vicm>Vdsat+Vgnp

Actually you could say gm=gmp+gmn is valid for the whole voltage supply range, even {GND-Vdiode .. VDD+Vdiode}, as one of the 2 summands --> 0 outside of its (above stated) activity range.

I am supposed to see the graph of this trend based on the book of Allen Holberg.

Sure; just plot the above equation. What's the problem?