these two mos are used as "floating current source" , they served as two "batteries " to bias the MOS of output stage in active regions with the small signals from the outputs of the first diff-amp stage. By doing this, the output stage will not go to states such as (active NMOS+triode PMOS) or (active PMOS+ triode NMOS) during the transient period which will conduct extra currents.
so they will go to states such as (active NMOS+cutoff PMOS) or (active PMOS+ cutoff NMOS) directly ,is it ? how about the state (active nmos+ active pmos)?