basics of JFET

Discussion in 'General Electronics Chat' started by chyadesh, Apr 10, 2009.

  1. chyadesh

    Thread Starter Member

    Apr 10, 2009
    19
    0
    can JFET can be used as a switching device rather than BJT's?


    or can MOSFET be used as a switching device rather than BJT's?


    can u list the principles , advantages, and applications of both CE and CB Amplifiers..?
     
  2. Wendy

    Moderator

    Mar 24, 2008
    20,766
    2,536
    The answer for the first two is yes, but what turns them on is different, from each other and from a BJT.

    The third is a bit long winded, more than I'm willing to get into at the moment. This sure looks like a homework question.
     
  3. Dave

    Retired Moderator

    Nov 17, 2003
    6,960
    144
    Common-emitter and common-base amplifiers have just gone active in the e-book:

    Common-emitter amplifier

    Common-base amplifier

    Have a read of these articles and post up your conclusions - members can then give you guidance on your answers.

    Dave
     
  4. miskol

    New Member

    Mar 20, 2009
    1
    0
    Field Effect Transistors can be used to replace normal Bipolar Junction Transistors in electronic circuits and a simple comparison between FET's and transistors stating both their advantages and their disadvantages is given below.

    Field Effect Transistor (FET) Bipolar Junction Transistor (BJT)
    1 Low voltage gain High voltage gain
    2 High current gain Low current gain
    3 Very input impedance Low input impedance
    4 High output impedance Low output impedance
    5 Low noise generation Medium noise generation
    6 Fast switching time Medium switching time
    7 Easily damaged by static Robust
    8 Some require an input to turn it "OFF" Requires zero input to turn it "OFF"
    9 Voltage controlled device Current controlled device
    10 Exhibits the properties of a Resistor
    11 More expensive than bipolar Cheap
    12 Difficult to bias Easy to bias
     
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