See Vmin and Io as illustrated. Io is arithmetically centered about Io which is 100 A. Ignore bulk effects and keep W/L’s between 1 and 100.

Vmin and Io are determined by simulation of your design once using the HIGH model parameters and once using the LOW model parameters. These two simulations are to be plotted on an iout versus vout plot as shown above. Vmin is the distance horizontally from the origin to where the line AB intersects the right-most IV curve. Iois the biggest vertical difference between the two simulations form Vmin to 5V.