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P-Channel MOSFET Switching

  1. Aug 5, 2010 #1


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    Hi all,

    I'm using 7 P-channel mosfets to switch different loads using 1 microcontroller on an electrical power and distribution system. My circuit is as follows for each of the 7 Mosfets.

    Gate: through a resistor to ground on microcontroller and through a High value (600 kilaohms)
    Drain: to load
    Source: I/O line from microcontroller and input power

    So all the gates are interconnected to the ground on the cpu

    The problem I'm having is that when I turn one mosfet on all the mosfets turn on and I can't figure out why. I am unable to use N-Channel mosfets. Any help on this matter would be very very appreciated
  2. jcsd
  3. Aug 6, 2010 #2
    Are you sending 0s or 1s from microcontroller to source of PMOSs when all of them gets turned on ?

    if the gate is connected to gnd, sending 0 to PMOS's source will turn it off, but sending 1 keeps it turned on all the time. I suspect that your microcontrollers are sending 1s to all the PMOSs.
    Last edited: Aug 6, 2010
  4. Aug 8, 2010 #3
    I don't understand what you have from your description. Can you post a schematic?
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