Simple Zener Diode Design

Discussion in 'Homework Help' started by jegues, Mar 17, 2011.

  1. jegues

    Thread Starter Well-Known Member

    Sep 13, 2010
    See figure attached for problem statement.

    I've been trying to work through this question but I can't figure out how they determine Iz.

    The Iz he seems to be determining seems to be more like IL to me. He's taking the voltage across the resistor (this voltage is identical to the volatge across the zener diode) and dividing it by the resistance of the load. Isn't this IL not Iz?

    If so, then we now know IL and know that we desire an Iz giving us a voltage of 7.5V, so Iz = 12mA as specified in the question, right?

    Why does he choose Iz = 3.7mA? This won't operate at 7.5V, right?

    Therefore the current from the source, I should simply be I = Iz + IL.

    What approach is he taking?

    EDIT: I managed to work through this one.
    Last edited: Mar 17, 2011
  2. hobbyist

    Distinguished Member

    Aug 10, 2008
    He selected 10mA. total,current through the resistor.
    So 6.25 of that flows to the load and the remainder would be (10mA - 6.25mA)
    Last edited: Mar 17, 2011