P Channel Mosfet ?

Discussion in 'The Projects Forum' started by jungleb0y, Oct 25, 2010.

  1. jungleb0y

    Thread Starter New Member

    Jan 27, 2010
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    Do they make a P Channel Mosfet that is off when the gate is + instead of -?
     
  2. rkovvur

    New Member

    Sep 16, 2010
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    In mosfet, the gate is always referenced with respect to the source. If your gate is at a higher voltage than the source, then Vgs is +ve. If gate is at a lower voltage than the source then Vgs is -ve.

    Usually for Pmosfet biasing, the source is connected to Vcc. So if you connect the gate to Vcc, then mosfet is Off because Vgs = Vg-Vs = Vcc-Vcc=0

    if you pull gate to Gnd, then Vgs = Vg-Vs = 0-Vcc = -Vcc. Then the mosfet is ON.

    hope this helps.
     
  3. beenthere

    Retired Moderator

    Apr 20, 2004
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  4. jungleb0y

    Thread Starter New Member

    Jan 27, 2010
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    Think I'll just go with a N Mosfet and convert it that way to run the P
     
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