Transistor selection guide

Discussion in 'General Electronics Chat' started by kammenos, Jun 3, 2009.

  1. kammenos

    Thread Starter Active Member

    Aug 3, 2008
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    I was struggling to purify an undervoltaged 3wire PC fan rpm signal (yellow wire). I tried several methods but under 600rpm, i always had problems. I tried 2n222 alone and darlington. I also tried some other transistors. And then, out of the sudden, i tried a transistor that just worked!

    What i want to result is, what criteria are there to choose a transistor?
    Is there a site and/or a book (that i would rather prefer) for transistor selection?

    Thanks again
     
  2. bertus

    Administrator

    Apr 5, 2008
    15,648
    2,347
    Hello,

    Here is an excelsheet with transistors.
    There are selection knobs on the top.
    (just unzip and open it in exel).

    Greetings,
    Bertus
     
  3. kammenos

    Thread Starter Active Member

    Aug 3, 2008
    127
    0
    PERFECT!!!!! THANX

    But i would like to know basically the way to choose. Some theory you know... How to choose hfe, what type of transistor, PNP or NPN? You know....
     
  4. kammenos

    Thread Starter Active Member

    Aug 3, 2008
    127
    0
    Please? Anyone?
     
  5. bertus

    Administrator

    Apr 5, 2008
    15,648
    2,347
    Hello,

    The transistor specification is dependent on the way you want to use it.
    There are a couple of questions you can ask for selecting a transistor.
    1) how many power has it to dissipate?
    2) how many current will the transistor have to handle?
    3) what is the working voltage?
    4) is the transistor used as amplifier or as a switch?
    5) what gain will be required?

    Greetings,
    Bertus
     
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