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Homework Help: Ideal diode question

  1. May 22, 2009 #1

    I am stuck trying to work out a problem involving two ideal diodes.

    http://img200.imageshack.us/img200/668/idealdiodev.jpg [Broken]

    I need to find V and I. Aswell as which diode is on and off.

    I have tried to solve it by assuming d1 is on and hence V is 0 but i cant get the right answers no matter what formula I try.

    Any help would be greatly appreciated.

    Last edited by a moderator: May 4, 2017
  2. jcsd
  3. May 23, 2009 #2
    Remove D2 from the circuit. Work out the voltages at the nodes where D2 was connected. Decide whether D2 would be forward or reverse biased. Proceed from there.
  4. May 24, 2009 #3


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    Welcome to Physics Forums.

    Um, no, you can't conclude V is 0 from assuming D1 acts as a short.

    Using the D1-is-on assumption, try solving the problem for both D2-is-on and D2 is non-conducting. See which assumption gives a consistent solution:

    If D2 is on, do you get a positive value for the current I? (I.e., the diode is forward-conducting)​
    If D2 is non-conducting, do you get a higher voltage on the left side than the right? (I.e., it is reverse-biased)​
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