Self-biasing JFET current source

  • #1

Homework Statement



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)

Homework Equations



0fcec9ef43a16a1e8e8fc5db3dcf3bfe.png


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.
 
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