I want to achieve- I need to understand how the circuit works.
The input voltage is applied varying from 5V to 200V which is connected to drain pin. The source pin is connected to zener voltage with zener voltage of 5.1V with Zener test current at 1mA.
Since the mosfet will turn ON only when Vgs > Vth , but in this circuit the voltage at Vs is not known. Can you guide me in understanding the working of circuit.
The output of voltage (5.1V) will be connected to LDO input pin to get the output voltage(3.3V) which can be connected to controller Vdd pin.
I am expecting the voltage to turn on the LDO, instead am not seeing any voltage at the Source pin.