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mosfets in critical condition

Discussion in 'Electronic Basics' started by [email protected], Oct 10, 2008.

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  1. Guest

    Let me guess... it's NOT normal for a mosfet to register < 40 ohms
    between D and S with no gate voltage applied...

    correct?

    Michael
     
  2. If the gate is floating it might? Or if it's depletion mode?
     
  3. Guest


    I've got IRF530 and an IRLZ34N mosfets.

    I noticed something was up when my power supply's current limiting
    circuitry deactivated the power supply.

    Debugging: one at a time, I connected the drain to a 12V light bulb,
    and tapped the gate with +12V. The light bulb turned on, and STAYED
    on even with the gate voltage removed. That's not supposed to happen,
    is it?

    At first I thought I had a bum IRF530, burned out from previous
    experiments, so I tried my IRLZ34... same thing...

    A TIP31A behaves as I'd expect it to though... turns on, then off when
    I remove voltage from the base...

    Transistor triage...

    Michael
     
  4. Guest


    Oh ok! I'll breadboard a test circuit that grounds the gate, and see
    if that fixes things...

    Thanks,

    M
     
  5. Eeyore

    Eeyore Guest

    Applied ? Sure there's not some charge on there already.

    Now try SHORTING the gate to the source.

    Graham
     
  6. Guest


    Ok, will do when I get home from work.

    Mosfets in critical but stable condition...

    How's the girl from the pub doing?

    Thanks,

    M
     
  7. Eeyore

    Eeyore Guest

    Will post to the original thread.

    Graham
     
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