MOSFET transistor question

Discussion in 'Homework Help' started by fran1942, Nov 4, 2010.

  1. fran1942

    Thread Starter Member

    Jul 26, 2010
    58
    0
    Hello, I am not sure of the answer to this question.
    Can someone please help me with the answer.

    "In an N Channel MOSFET, which terminal is at the most positive voltage when the switch is ON ?"

    Thanks kindly.
     
  2. hgmjr

    Moderator

    Jan 28, 2005
    9,030
    214
    Your title refers to a BJT yet your question is about MOSFETs.

    You should be able to find the answer to your question with a bit of web searching using google.

    hgmjr
     
  3. fran1942

    Thread Starter Member

    Jul 26, 2010
    58
    0
    sorry, I do mean MOSFET.

    I have searched and I think the answer is that the drain is the most positive terminal of a MOSFET both in switch on and switch off position.

    Can someone please confirm if I am correct ?

    Thanks.
     
  4. hgmjr

    Moderator

    Jan 28, 2005
    9,030
    214
    I edited the file per you comment.

    hgmjr
     
  5. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
    6,357
    718
    The drain is usually slightly more positive than the source when ON, but I believe you are neglecting how the MOSFET gets turned ON.
     
  6. Engr

    Member

    Mar 17, 2010
    114
    5
    When an N-ch MOSFET is OFF, the DRAIN is more positive than the source but once the N-ch MOSFET is turned ON, the DRAIN and the SOURCE is ideally shorted. But in reality, when a MOSFET is turned ON, there is a small resistance developed between the DRAIN and SOURCE. This is called the Rdson. There will still be a small voltage drop accross the DRAIN and the SOURCE so for an N-ch MOSFET (ON or OFF) the DRAIN is always more positive than the SOURCE.
     
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