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Homework Help: Mosfet circuit

  1. Mar 15, 2010 #1
    i have a mosfet circuit question
    since my prof. didn't explained much about the mosfet im pre lost..
    during the lecture..he show us two circuit diagram..
    the mosfet circuit
    and this regular circuit..

    and he ask us why the above equivalent circuit model is a valid representation of the mosfet circuit.
    and i don't know how this regular circuit is related to mosfet circuit..
    plz explain to me..

    by the way.. in the mosfet circuit
    c is the wiring capacitance and CGS of following gate
    Last edited: Mar 16, 2010
  2. jcsd
  3. Mar 16, 2010 #2


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    Staff Emeritus
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    Gold Member

    A MOSFET can act like a switch. When the gate voltage is low (below a certain threshold), the drain and source are not electrically connected, and so the transistor does not conduct (this is equivalent to the switch being open). When the gate voltage is high (above a certain threshold), there is a conductive pathway between drain and source (which is equivalent to the switch being closed). But it won't be a perfect conductor. There will be certain resistance between drain and source that appears when the transistor is "on" and conducting. This resistance is represented by RON. I shouldn't say more.
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