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Homework Help: Diode Circuit Problem

  1. Oct 18, 2007 #1
    1. The problem statement, all variables and given/known data
    See attachment

    2. Relevant equations
    We are to assume the voltage drop across diodes is .7v (don't use the diode equation!).

    3. The attempt at a solution

    I first was assuming that both diodes were "on". Then my work is as follows:

    V1 is the voltage directly above diode D1 (the left most diode)...

    [tex]I+ \frac{V_{1}-.7-(-5)}{5k\Omega}=\frac{5-V_{1}}{10k\Omega}[/tex]

    [tex]I+ \frac{.7-.7+5}{5k\Omega}=\frac{5-.7}{10k\Omega}[/tex]


    Now since I is negative, one of my assumptions is wrong? So now I assume the rightmost one is "off" (D2).

    So.. then
    Solving for I
    [tex]I = \frac{5-.7}{10k\Omega}[/tex]

    [tex]I = .43 mA[/tex]

    Solving for V
    Well.. since theres no current, v=-5?

    Am I approaching this correctly?

    Attached Files:

    Last edited: Oct 18, 2007
  2. jcsd
  3. Oct 20, 2007 #2


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    Staff Emeritus
    Science Advisor
    Gold Member

    You're on your way. In this second case, what would be the value of V1? Does this agree with your assumption?
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