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Homework Help: Simple Diode Analysis Problem - Calculating Current/Voltage in a diode:

  1. Jan 29, 2012 #1
    1. The problem statement, all variables and given/known data

    Refer to the figure attached. Let IS = 25 fA and VCC = 10V. What is the total current, the current in the diode, and the current in the 5KΩ resistor? What is VD? Use the iteration technique.

    2. Relevant equations

    Ideal Diode Equation: I = Is(e^(Vd/Vt) - 1)
    Ohm's Law: V= IR
    Thermal Voltage: V = kt/q = 25.9mV

    3. The attempt at a solution

    Total Current in the circuit = 10 V / 10kΩ = 1mA

    We need to find the Vd and Id using the constant voltage model and then use the iteration method using the ideal diode equation to get closer and closer to Vd and Id using iterations.

    I am not sure how to analyze the circuit using the constant diode equation. I know how to use the iteration method.

    Current through the diode = Current through the 5kΩ resistor.

    Please help - Any suggestions will be helpful.

    Thank you!

    Attached Files:

  2. jcsd
  3. Jan 30, 2012 #2


    User Avatar

    Staff: Mentor

    Why don't you begin by finding the Thevenin equivalent for the the voltage source Vcc and the resistors? This will leave you with a simple series circuit:


    Attached Files:

    • Fig1.gif
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