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NPN Transistor

Discussion in 'General Electronics Discussion' started by MAHABA, Jul 5, 2012.

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  1. MAHABA

    MAHABA

    14
    0
    Apr 13, 2012
    Hi everybody,,

    I connected a circuit as showen in the figure below>>

    [​IMG]

    The problem is that the circuit works fine for some transistor such as C1815 and BC547, but for others such as C8050, C8550, C945 and A1015 it does not work any more.

    Q1: Why this circuit is working for some transistors only??

    Q2: Is this circuit is not a good way of biasing (I want the LED to be on only!)??

    Q3: Is there a better way of biasing, in consideration of min num. of resistors??

    Thanks a Lot!!
     
  2. CocaCola

    CocaCola

    3,635
    5
    Apr 7, 2012
    Are you minding the emitter/base/collector orientation, they flip flop orientation between the transistors you have listed...

    You should also put a resistor on the base so that you don't kill it with too much current...

    From a quick Google image search...

    C1815 - E C B
    BC547- C B E
    C8050 - E B C
    C8550 - E B C
    C945 - E C B
    A1015 - E C B
     
    Last edited: Jul 5, 2012
  3. MAHABA

    MAHABA

    14
    0
    Apr 13, 2012
    Hi CocaCola,,
    It is right I am considering the terminals for each transistors, but way for C1815 and C547 it works and for the reset it does not work??

    Thanx
     
  4. CocaCola

    CocaCola

    3,635
    5
    Apr 7, 2012
    They should all work, but you may have damaged them without limiting the current to the base...
     
  5. gorgon

    gorgon

    603
    24
    Jun 6, 2011
    Put a 10k resistor in series with the base. You are burning off the base emitter diode.

    TOK ;)
     
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