Common source amplifier with current mirror active load
The bias current is set by the current source Ibias, it is mirrored to the active load Q2 and the current through Q1 has to be about equal to the current delivered by Q2.

This is not done by some sort of bias network but through application of feedback. Imagine this stage as the second stage of an OpAmp as shown below.


The CS Stage consists of M3 and M8, biased by M1.

In order to use this Opamp feedback is required. For example OUT could be fed back to IN-. The first stage of the OpAmp will take care of the biasing. The voltage at the gate of M8 will be such, that OUT is almost equal to IN+.