I am probably being stupid and should probably go to bed but how is current flowing in this circuit below?
From my understanding, a P-channel MOSFET allows current to flow when its gate terminal is at a lower potential than its source terminal. Of course a certain threshold must be met to fully "turn on" the channel but regardless. What I don't understand with this circuit is how the capacitor is able to charge. As can be seen from the graphs, the VGS starts at 0V. VGS = 0V means that the gate and source are at the same potential, thus from the earlier criterion, current should not flow. However, it does flow and charges the capacitor to the source voltage. What is going on here?
I found this kind if configuration in reverse polarity protection circuit as picture below.
First the current flow from drain terminal through body diode or intrinsic diode. After that source terminal got voltage as drain minus by diode’s forward voltage drop. Then the body that connect to source has some positive charge that build the channel along with gate plane. The channel is just N-type with charge density created by electric field from gate that allow current pass through in bidirectional. At this point, the voltage dropped across source and drain is lower than diode’s forward drop.