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Pn - junction diode experiment - varying heat

  1. Mar 16, 2011 #1
    1. The problem statement, all variables and given/known data

    This isn't exactly a problem, but I need help with an experiment. I've got to design an experiment to show a) the variation of voltage with a diode when the diode is in forward bias
    b) The variation of current (i think) with heat, keeping voltage constant.
    The thing is I'm not sure how to design the part 'B' experiment, and I also have to predict the graph that will be generated from the output.

    2. Relevant equations

    I'm pretty sure I've got to use I = Io exp (eV/2kt) where
    I = Current,
    Io = Max current at absolute zero,
    e= charge on an electron
    V= voltage
    k = Boltzmann's Constant
    t = Temperature in Kelvin.

    3. The attempt at a solution

    For a)
    I set up the circuit with a 1.5 V D.C supply connected in series with a rheostat, milliammeter and the diode in forward bias and a voltmeter in parallel with the diode. I varied current and measured the corresponding voltage (making sure to keep the current low, <50 milliamps)
    I had to ln the equation to make the ln I - V graph linear (for experiment a)

    ln I = Ln Io + (eV/2kT)
    with Ln I on the Y axis and V on the X.
    This made a linear graph and allowed me to calculate the value of e from the gradient, compare it to the standard and derive the percentage error of my experiment a.

    I need to do something similar with b)

    Any help will be greatly appreciated.
    Also, this is my first post so I'm really sorry for any faux-pas.
  2. jcsd
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