While i was searching about accurate circuits to sense currents in high side, i found a very interesting circuit proposed by linear technoloy, but i didn't understand the role of the NMOS at the output.
What i understood is that the current that flows on the Nmos and the output resistor is : Vshunt/Rin tthen the output voltage is : Vshunt*Rout/Rin.
The problem is that i thought that the op amp wasn't operating in the linear zone, but when i simulate it i found that the it is operating in the linear zone.
The second problem is that the voltage on the NMOS (VDS) is the same as the common mode and i thought that it would be 0V ( since the current flows into it )
So my question is how this circuit functions generaly ? Thank you for your help.