Are these just two transistors? (schematic query)

Discussion in 'General Electronics Chat' started by deki, Oct 10, 2011.

  1. deki

    Thread Starter New Member

    Sep 6, 2011
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    Last edited: Oct 10, 2011
  2. debjit625

    Well-Known Member

    Apr 17, 2010
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  3. deki

    Thread Starter New Member

    Sep 6, 2011
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    Sorry! I forgot to post the link (it's there now) :/
    But yes, now that you mention it, it is a Darlington pair transistor. Thanks.
     
  4. debjit625

    Well-Known Member

    Apr 17, 2010
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    They come in one single package,so the circle represent a Darlington pair in this case its BD679.
     
  5. deki

    Thread Starter New Member

    Sep 6, 2011
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    ^^But the PWM circuit would still work if I just used two transistors and connected them in such a configuration?
     
  6. debjit625

    Well-Known Member

    Apr 17, 2010
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    Yes, Darlington pair could be made by single transistors connecting in that way, but those packages are specially designed to improve its performance. So use a Darlington package rather making one...

    Good Luck
     
  7. deki

    Thread Starter New Member

    Sep 6, 2011
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    Thanks for that.
     
  8. Wendy

    Moderator

    Mar 24, 2008
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    Another similar transistor configuration is the Sziklai Pair

    Both are high gain configurations, where the total beta equals the two beta multiplied.

    Both act like a single transistor.

    Both will drop a minimum of 0.6VDC in saturation on the CE equivalent.

    The Darlington Pair will drop 1.2VDC on it's equivalent BE.

    The Sziklai Pair will drop 0.6VDC on it's equivalent BE.
     
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