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Homework Help: Self-biasing JFET current source

  1. Feb 13, 2010 #1
    1. The problem statement, all variables and given/known data

    For the self-biasing JFET current source in Figure (http://sound.westhost.com/ab-f5-2.gif), what prevents this circuit from reaching the characteristic curve (showing ID vs. VDS) where VGS equals zero? The answer has to do with the self-biasing aspect of this circuit. What would happen to the value for VGS if the source resistor, R1, is changed to 100 ohms? Would it increase, decrease or stay the same?
    (The "LOAD" in the figure is a 10k pot)

    2. Relevant equations

    0fcec9ef43a16a1e8e8fc5db3dcf3bfe.png

    3. The attempt at a solution

    For the first part I said there is no guarantee that Vgs is zero because of R1. (There will always be a voltage drop) But I don't know how to link it to the self biasing aspect.
    For the second question I think the Vgs value will increase since less resistance=more current.

    Please correct any false assumptions/approach to this problem.
     
    Last edited by a moderator: Apr 24, 2017
  2. jcsd
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