What is the purpose of using a power MOSFET in the main voltage input of a circuit? Why not just directly connect the main voltage input to a power supply? Why go through the MOSFET?
I am trying to understand a circuit that goes directly from a 12V battery to Drain of a P-channel power MOSFET. The Gate is connected to ground through a 1MOhm resistor and connected to Source through a Zener diode. The circuit is connected to the Source pin.
Accidentally reverse the battery. Repeat your circuit analysis. Illumination should follow.
That is a protection against the battery reversal. Mosfet has less of the voltage drop compared to a diode.
Vladimir Vassilevsky DSP and Mixed Signal Design Consultant
And when analyzing, remember the 'parasitic' drain-source diode inside the MOSFET - it is an essential part of the trick...
Arie
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Thanks again for the help!
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