This is a cascode current mirror. Assuming that all transistors are idential so that Iin equals Iout.
With the current, the gate to source voltage of all transistor are equal and it is Vgs.
Now I am confused about how Vgs of transistor Q4 is established by Iin or Iout.
For transitors Q1, Q3, they are diode connected transistors (feedback between input and output), so the current Iin is converted to the gate source voltage Vgs.
This is easy to understand. The diode connnected transistor is something like current to voltage converter here.
However, how the voltage Vgs of Q4 is established by the current In or Iout?
I don't see any kind of feedback here so that the output current Iin or Iout can be converted to its input voltage Vgs.
Could anyone explain what is happening here? How Q4 converts its current into the gate source voltage Vgs?