want to know about mosfet

Discussion in 'The Projects Forum' started by shindehari, May 19, 2014.

  1. shindehari

    Thread Starter New Member

    May 19, 2014
    3
    0
    when i trying to connect p-channel mosfet source to 10v +ve supply and drain to ground through cro and the cro reading is the supply voltage, there is no trigger to the gate terminal. so, my question is that without applying gate trigger why it is conducting and giving output to the drain. so give me conceptual answer of my question

    thank you
     
  2. jerluwoo

    New Member

    May 17, 2014
    6
    1
    A mosfet can be made to conduct by simply touching a meter probe to the gate pin, in fact this a way to test that a mosfet is good. First test short all leads together then check for continuity between source and drain without touching the gate. It should not conduct. Then charge the gate by touching the meter probes to the source and gate, polarity depending on N or P channel, and testing that the source to drain now conducts.
     
  3. JDT

    Well-Known Member

    Feb 12, 2009
    658
    85
    The MOSFET must not be operated with the gate not connected.

    Connect the gate to the source with a resistor. This can be quite a high value: 1MΩ or more.

    Because the gate is insulated it can pick-up a static charge that can cause the MOSFET to conduct.

    The mosfet can be damaged if the gate - source voltage is greater than about ±15V.
     
  4. DickCappels

    Moderator

    Aug 21, 2008
    2,659
    632
    You should have a load of some type; MOSFETs leak between the drain and source, so a load is needed to make the resulting voltage very low.
     
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