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    Cut-off current through an N-channel power MOSFET with negatively charged gate

    How low can such current be?

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    Re: Cut-off current through an N-channel power MOSFET with negatively charged gate

    Hi,

    Maybe low microamperes, maybe in the nanoamperes region.
    It depends on a lot of parameters ... and mainly on the part you use.
    I expect a 100mA rated MOSFET to have less current than a big 250A MOSFET.

    Why do you ask? What's the application, problem or idea?

    Klaus
    Please don´t contact me via PM, because there is no time to respond to them. No friend requests. Thank you.



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    Re: Cut-off current through an N-channel power MOSFET with negatively charged gate

    How low it "can" be is immaterial, how high it might be is
    more relevant to circuit design if you're not hand-picking
    parts for that quality.

    GIDL (gate induced drain leakage) is a thing in some types
    of MOSFETs (though I've seen it more in integrated, plain
    FETs). That means after some distance into negative Vgs,
    drain current increases from its minimum.



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    Re: Cut-off current through an N-channel power MOSFET with negatively charged gate

    Quote Originally Posted by dick_freebird View Post
    How low it "can" be is immaterial, how high it might be is
    more relevant to circuit design if you're not hand-picking
    parts for that quality.

    GIDL (gate induced drain leakage) is a thing in some types
    of MOSFETs (though I've seen it more in integrated, plain
    FETs). That means after some distance into negative Vgs,
    drain current increases from its minimum.
    I am clearly asking about MOSFETs, so gate current should be much smaller than drain current.



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    Re: Cut-off current through an N-channel power MOSFET with negatively charged gate

    Quote Originally Posted by htg View Post
    I am clearly asking about MOSFETs, so gate current should be much smaller than drain current.
    Gate curreent is always very low and independent of drain voltage, since the gate looks like a capacitor.

    What is the perceived problem you have?
    Zapper
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    Re: Cut-off current through an N-channel power MOSFET with negatively charged gate

    Quote Originally Posted by crutschow View Post
    Gate curreent is always very low and independent of drain voltage, since the gate looks like a capacitor.

    What is the perceived problem you have?
    In the response of dick freebird above there is the statement:

    "GIDL (gate induced drain leakage) is a thing in some types
    of MOSFETs (though I've seen it more in integrated, plain
    FETs). That means after some distance into negative Vgs,
    drain current increases from its minimum."

    My original question is: what is the drain current in an N-channel MOSFET with maximally negatively charged gate?
    Lets assume we are dealing with a power MOSFET, Idmax=100 A.



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    Re: Cut-off current through an N-channel power MOSFET with negatively charged gate

    Quote Originally Posted by htg View Post
    I am clearly asking about MOSFETs, so gate current should be much smaller than drain current.
    Sure, if you were clear, but you were not. Just what is
    "cutoff current" supposed to mean to the average person
    schooled in the art? Drain current, unless you say otherwise.
    You didn't until this #4 post.

    Short of breakdown there will be some gate leakage which
    the manufacturer only specifies a one-sided (max) limit
    for, and quite often only for the "on" condition Vgs(max)
    (expecting the user to not overdrive the gate, as this can
    pose other problems as well).

    There's no answer for MOSFETs generically. Gate oxide
    thickness, quality, area and the effects of field control
    structures (i.e. how much field the oxide sees, under
    operating conditions) all matter. And all of them are device-
    design as well as wafer-shot specific.

    If you had -a- device in mind the datasheet would give
    you some guidance about the corners of the "box".

    And for the power MOSFETs which incorporate a gate
    protection diode, which are some, all of this goes out
    the window.

    Now in post #6 you're back to drain current which is what
    I told you about originally. Which is certainly dependent on
    drain voltage and temperature. All of which you'd look to the
    specific product datasheet, to say - not ask people to make
    up an untethered guess.



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