Fig 3. shows the simulation result of gmT versus input
common mode change with the transistors dimensions given
in Table I.
It can be observed from Fig. 3 that the gmT value is
changing only maximum +25% around specific ±0.75V input
common-mode values.
Transistors M31 and M32 are two common drain stages to
achieve high current gain from the voltage gain exist at the
high impedance nodes-drain nodes of M20 and M21.