Hello,

I think what you need to do is called pareto diagram, which shows the tradeoff between different performance parameters.

but first let us discuss the testbench which should be used

1.  you should fix the frequency you are going to use in simulation.

2.  Set  transient analysis using an input sinsoidal wave source and the frequency you defined.

3. This transient simulation should run several times using parametric analysis in which you sweep an optimization parameter, which may be the size of the cascoded transistors as I understood or anything else.

4. Plot the output then you will have what is called a family (group of waves)

5. If you are using cadence then use the calculator and the special functions to define the  gain and the swing, and plot them versus the optimization parameter.

6. You will have two waves, one representing the gain and the other representing the swing.

7. Plot them against each other, I am not sure if the calculator can do it or not and this should be the Pareto diagram.

8. Another solution,  I think you can define a weight function ( W(gain,swing)= A*gain + B*swing ) which is the sum of the both gain and swing with adjusting a weight for each of them and try to optimize this function to what you need.  

I hope this would be helpful.

amar