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The collector current

  1. Sep 25, 2015 #1
    1. The problem statement, all variables and given/known data
    In my book ,I found this line which says ,"The collector current comprises two components-the majority and the minority carriers .The minority-current component is called the leakage current and is given the symbol ##I_{CO}## .The collector current, therefore is determined in total by $$I_C=I_{C_{majority}}+I_{CO_{minority}}$$
    For general purpose transistors, ##I_C## is measured in milliamperes and ##I_{CO}## is measured in microamperes and nanoamperes."

    2. Relevant equations

    We know that major part of the emitter current goes into the collector current (npn transistor). And therefore, emitter and collector currents are in milliamperes and base current is in microamperes.

    3. The attempt at a solution

    The confusion here I face is due to the majority and minority in subscript. We know that the holes in the collector are the minority carriers, but they are the cause of considerable collector current. But according to this equation the "majority" current is in milliamperes and the minority current is in microamperes. This doesn't make sense. What is wrong with my thinking here?
     
    Last edited by a moderator: Sep 25, 2015
  2. jcsd
  3. Sep 26, 2015 #2

    ehild

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    You answered your question already. The Base-Collector diode is reverse biased, so the minority carriers (holes) go from the collector to the base and electrons from the base to the collector. But the base has not only its own minority carriers, but also those, coming from the emitter. For them, the potential of the collector is attracting. They mean the main component of the collector current.
     
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