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Calculating Is and nVt for Silicon Diode, How?

  1. Mar 15, 2012 #1
    Hello, everyone!

    I was asked by my lab instructor for an Electronic course to conduct a diode experiment by which I can get the value of (nVt) and saturation current (Is) for that diode.

    I did the experiment by connecting a DC power supply in series with a forward-biased silicon diode (1N4007-MIC), and a 1Kohm resistor. I took voltage reading across the diode starting from 10V DC supply, down to 1V. Now, I have the readings, plus I calculated the diode current (ID) for each -1V difference in DC supply. Also, I graphed a curve of I-V characteristics.

    Well, I understand that to get the value of nVt and Is, I have to take two values on that curve, an upper value of VD(V2) on the horizontal axis corresponding to an upper value of ID(I2) on the vertical axis, and a lower value of VD(V1) corresponding to a lower value of ID(I1). I take these values and substitute in the equation:

    V2-V1=2.3nVt log(I2/I1) --> From this, I can calculate the only unknown value which is nVt.

    I take the resulting value and substitute in the equation:

    I=Is e^(V/nVt) --> From this, I can calculate the only unknown value which is Is.

    So, my question is, is my understanding to how to get the two values correct? is there any shorter and easier way to get them?

    Also, where can I find the the two values in the diode's datasheet? I looked up for it but didn't find any indication of it (this datasheet for example).

  2. jcsd
  3. Mar 15, 2012 #2


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    Staff: Mentor

    Hi CDTOE! http://img96.imageshack.us/img96/5725/red5e5etimes5e5e45e5e25.gif [Broken]

    It looks fine. Take more than just 2 readings off the graph, and determine an average of your nVt estimates.

    You might have to deduce them from the typical V-I curve provided?
    Last edited by a moderator: May 5, 2017
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