I bought some IRFD9024 p-channel MOSFETs, and for some reason there seems to be a diode drop from the SOURCE to the DRAIN. As far as I understood it, the body diode is from the DRAIN to the SOURCE as illustrated by the datasheet:

enter image description here

To provide some context, here is my complete circuit. It uses a push button to short the capacitor, after which the voltage slowly increases again, providing a chosen amount of time for the regulator to deliver 5V to a microcontroller.


simulate this circuit – Schematic created using CircuitLab

  • 2
    \$\begingroup\$ Your circuit looks correct, other than the strain on the switch and cap when you push on the switch (I recommend a 100 to 1000 ohm resistor in series with the switch). Double-check that you haven't hooked the part up backwards, and that your supplier hasn't accidentally (or negligently, if it's eBay or some other shady source) supplied you with N-channel FETs. \$\endgroup\$ – TimWescott Dec 9 '18 at 17:58
  • \$\begingroup\$ What is your actual question? The body diode is BETWEEN drain and source. Also can you be clear about which FET you are using? \$\endgroup\$ – Andy aka Dec 9 '18 at 17:59
  • \$\begingroup\$ I have not really worked with P-channel MOSFETs aside from in theory, that's why I'm asking. So my question I suppose is, "am I missing something obvious here?". As for the part, I will upload a picture shortly. I acquired it from my local electronics shop (not sure where they get it from). The datasheet I've posted is the one they used on their website. \$\endgroup\$ – Chris-Al Dec 9 '18 at 18:08
  • \$\begingroup\$ The chip reads: IRFD A6I*RW5 9024. It looks exactly like the one in the datasheet \$\endgroup\$ – Chris-Al Dec 9 '18 at 18:19
  • \$\begingroup\$ What makes you think the body diode is reversed? How does your circuit behave differently than what you expect? \$\endgroup\$ – Elliot Alderson Dec 9 '18 at 18:58

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