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Homework Help: Semiconductor light-emitting diodes

  1. Jan 11, 2006 #1

    smn

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    Hello, i have a revision question that i'm only part-able to answer.
    The question is:
    Explain why an LED operating at a fixed current would be more stable than one operating at a fixed voltage.Consider the effect of the device heating on the IV characteristics.Explain under which condition there would be positive or negative feedback from the from the heating.
    What i can answer:
    If an LED is operating at a fixed voltage, then only small changes in voltage will result in large changes in current.Therefore it's better to fix the current because small changes in current won't cause large changes in voltage.
    If anyone could point me in the right direction for the other parts it will be much appreciated.
    Regards
     
  2. jcsd
  3. Jan 11, 2006 #2

    berkeman

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    Staff: Mentor

    Start with the equation for light output versus junction current. Look at any temperature related effects in that equation, and then look at the equation for the current versus junction voltage and the temperature effects there.
     
  4. Jan 14, 2006 #3
    This might require more research, but isn't a diode a current-controlled device?

    MLH
     
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