Confusion regarding pinch off voltage in a JFET

  1. I can't figure out what actually is the Pich-off voltage of a JFET.
    I basically have confusion between these two definitions:
    1. Pinch off voltage is that gate source voltage at which there is no drain-source current
    2. Pinch of voltage is that 'Drain-Source' voltage after which the drain source current becomes almost constant(saturates).
    If there is some other accurate definition for pinch off voltage,Please tell me.
    Also i want to ask that what is pinch off region?
    Thanks
     
  2. jcsd
  3. Here you find answer what is pinch off region.
    http://www.electronics-tutorials.ws/transistor/tran_5.html

    So the proper definition of a Pich-off voltage is
    Pinch of voltage is that 'Drain-Source' voltage after which the drain source current becomes almost constant(saturates).
    And for n-channel JFET Pich-off voltage is positive. But because Vgs(off) (the gate source voltage at which there is no drain-source current) voltage is negative and by accident equal to the magnitude of the pinch off voltage. Hence:
    |Vgs(off)| = |Vp| the magnitude of the pinch off voltage is equal to Vgs(off).
    And this is why we can say that |Vp| = |Vgs(off)| but in the same time Vp is a saturation voltage.
    But the only difference is the minus sign. Because Vgs(off) is negative but Vp is positive.
     
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