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Transistor Gain

Discussion in 'General Electronics Discussion' started by MAHABA, Aug 31, 2012.

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    Apr 13, 2012
    Hi guys,,

    How to know the transistor gain when designing for npn transistor??

    I dont know the collector current, I only know base current !!!

    In the data sheet there is no specific number for the gain!!

  2. john monks

    john monks

    Mar 9, 2012
    Datasheets typically use a term call "beta" or "HFe" to describe gain".
    And this is current gain. The number represents the collector current divided by the base current. Typically this number will be around 10 to 300.
    The gain of a transistor with a beta of 100 with a base current of 1mA will have a collector current of 100mA.
  3. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    Jan 21, 2010
    Of course the hfe only describes the maximum gain.

    Depending on your circuit, you may get a lower gain (in fact most often in linear applications you will want to control the gain).
  4. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

    Nov 28, 2011
    If you want any really useful answers, you need to explain a lot more about what you're doing.

    Can you post a schematic? Can you tell us why you need to know the number? Do you have a particular transistor in mind? Are you designing a circuit to work to a particular specification? We're playing tennis in the dark with you unless you give a lot of background information.
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