I have to find the feedback polarity. I proceeded as follows : 1. As Iin = iF , increasing Iin will increase iF 2. Now drain current for MF is increasing so Vgs of the transistor should increase 3. That means increasing Iin increase Vout 4. Now as Vout increases the current through RD2 decreases and all current through RD2 will flow through M2 , this means drain current through M2 is decreasing 5. This will cause gate voltage of M2 to decrease, this will cause current through RD1 to increase which means drain current through M1 increasing which further implies that gate of M1 or drain of MF increasing Now in short i found that increasing Iin will cause drain voltage of MF to increase Now my question is how to proceed further ???