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Mosfets Biasing Enhanced-Type Mosfets?

  1. Jun 15, 2012 #1
    Simple Question: Do Enhanced-Type Mosfets (And not Depletion Type ones) have Fixed Bias Configuration? If yes how do we draw the transfer curve? And locate Q point?
    (I didnt seem to find it in the book, only present for Depletion types)
  2. jcsd
  3. Jun 15, 2012 #2
    It is not advisable to use a fixed voltage to bias an Enhancement MOSFET. The turn on voltage is very unpredictable, it can vary a lot between parts. Also temp. drift is very large. You have to use source resistor degeneration to stabilize the current.

    Case in point, propagation delay in CMOS logics change quite a bit with temperature. This is because the switching threshold drift with temperature and the propagation delay change because of the rise time of the driving output. I had to design the critical timing circuits with bipolar logics.
  4. Jun 15, 2012 #3
    Thanks yungman, that's what I foresaw.
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