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NPN / N-channel

Discussion in 'Electronic Basics' started by Matt Krass, Feb 17, 2007.

  1. Matt  Krass

    Matt Krass Guest

    I'm diving back in to discrete component circuit design again after a
    few years, and I'm blanking out, is there any functional difference
    between an n-channel transistor and an NPN, same for p-channel PNP
    transistors?

    Thanks.
     
  2. Phil Allison

    Phil Allison Guest

    ** Worried Groper alert !


    ** The word "channel" implies the device is a FET ( Field Effect
    Transistor).

    Lots of interesting differences between a FET and a BJT (ie Bi-polar
    Junction Transistor)

    Do a Google search......



    ........ Phil
     
  3. DJ Delorie

    DJ Delorie Guest

    *If* the device is a MOSFET (and not a JFET), you can *almost* treat
    them the same as BJTs, at least for switching.

    Similarities:

    drain = collector
    source = emitter
    gate = base

    driving base relative to source enables current from drain to
    source.

    Differences:

    BJTs are current controlled current devices.
    MOSFETS are voltage controlled resistor devices.
    The response curve is different.

    So, where driving a BJT with a base current (Ibe) enables a much
    larger collector current (Ice), driving a MOSFET with a gate voltage
    (Vgs) reduces the drain-source resistance (Rds). Also, the gate has a
    small capacitance, so you not only have to drive it ON, but you have
    to drive it OFF too. The capacitance also affects the frequency
    response, so model it if you're doing high frequency work.
     
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