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Complementary pair transistors

kilwan

Jul 18, 2013
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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 ) ?
 

shrtrnd

Jan 15, 2010
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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).
 

shrtrnd

Jan 15, 2010
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Examples of complementary transistor pairs:
2N3055(NPN) 2N2955(PNP)
2N2222(NPN) 2N2907(PNP)
2N3904(NPN) 2N3906(PNP)
 

kilwan

Jul 18, 2013
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Jul 18, 2013
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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.
 

shrtrnd

Jan 15, 2010
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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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