Can you please explain how can I analyze and equate its feedback?
I have simulated it in LTspice as follows:
I have tried for 0.5A and Vout is precisely 2, half of above, so it is working, despite not according to the 5V/A expected. (Where is that missing volt?)
Vout and Vdrain are overlapped, and obviously Id = Is.
Also, I have noticed that in any case, Vgate (op amp output) is always saturated to Vsupply, so how is there any feedback? I thought from Vout equation that gain is R1/R2, then Vgate over R3 dictates sensitivity, but it doesn't seem like that.
Can you analyze it step by step to eq.: Vout = (R1/R2) * R3*Il?
EDIT: new simulation:
V(v+)-V(v-) = 550.4 mV
V+ = 4.55 V
V(vout) = 4.597 V
V(gate) = 5.191 V
V(gate)-V(vout) = 593.77 mV
I(R1) = 5.40 mA
I(R2) = 919.44542 µA
Ix(U2:OUT) = -6.323833 mA