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Complementary pair transistors

Discussion in 'Datasheets, Manuals and Component Identification' started by kilwan, Jul 18, 2013.

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  1. kilwan

    kilwan

    2
    0
    Jul 18, 2013
    Hi guys,

    I'm making an class-AB power amp. for school. Calculations and the simulation are done, but I need a pair of complementary transistors. Do you know of some shop that's selling those, accepts PayPal and is shipping worldwide (Yea, I'm kinda picky :p ) ?
     
  2. shrtrnd

    shrtrnd

    3,821
    519
    Jan 15, 2010
    You just need to check data sheets.
    Complementary pairs, just means one is a PNP and the complement is NPN. (With complementary specifications).
    There are a lot of those around.
    I'm wondering if you're thinking about 'selected' pairs, which are sold in sets of two or
    more, that just means they're the same transistor, but that they're tested to match one
    another in specification as closely as possible.
    Somebody will probably give you examples of complementary transistors. If I get some
    time, I'll follow-up with a post of some examples (after I, check some data sheets).
     
  3. shrtrnd

    shrtrnd

    3,821
    519
    Jan 15, 2010
    Examples of complementary transistor pairs:
    2N3055(NPN) 2N2955(PNP)
    2N2222(NPN) 2N2907(PNP)
    2N3904(NPN) 2N3906(PNP)
     
  4. kilwan

    kilwan

    2
    0
    Jul 18, 2013
    Oh, my bad ... I need those 'selected' pairs you're talking about. Mainly BD138 and BD140, but really, almost any pair of power transistors would work. Now the thing is that buying power transistors one by one and keeping fingers crossed that they'll have the same beta and so on is quite pricy. Well, atleast where I live :p .... That's why I'm looking for those 'selected' pairs.
     
  5. shrtrnd

    shrtrnd

    3,821
    519
    Jan 15, 2010
    Heck, we did that in school forty years ago. (But I obviously don't remember the circuit).
    Commercial parts suppliers don't bother selling selected pairs. It's something you
    usually have your techs do for you when you're producing products.
    Finding the Beta (gain) is pretty simple from what I remember. Then you can select
    the closest values of whatever group of transistors of that type you have.
    Can't help you with the test circuit. Maybe someone else here can. If you know what
    transistor you plan to use, check the data sheet and see if you can find a test circuit
    to determine Beta, or an applications sheet on the transistor for a Beta test circuit.
    With a transistor in mind, you can probably Google a test circuit to dermine Beta.
    Good luck. If you asked me this question forty years ago, I would have had the answer
    in my notes.
     
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