Used to sink or source current.
Amplification factor is given by the n-times width of output MOS compared to input MOS.
Exeample :
Input width = 20nm
Output width = 40nm
Iref : 100uA
Iout = (40/20) * 100 = 200uA
You can even use the grid voltage of a branch to drive other branches with different width.
There is a 2-stage MOS in this topology to compensate for transition voltage (Vt) and be as accurate as possible.
