Author Topic: Determining PNP collector and emitter  (Read 1489 times)

Torgoslayer

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Determining PNP collector and emitter
« on: February 25, 2016, 05:07:56 PM »
I've been finding too much conflicting information to continue. Need your expertise. I found some germanium transistors and can't find a datasheet for them. they are marked "Mullard OC42 Brittish Made". I've been reading articles and watching videos, about 20 in total and have learned how to use the diode checker  on my multimeter to determine pnp or npn. These are pnp. I can also identify slight difference in voltage drop between either collector-base and emitter-base. What is conflicting is every other lesson states that the higher voltage drop is EITHER. As in half say the emitter is the higher reading, and half state the collector is the higher reading, for both pnp or npn. This is driving me nuts. Please help me learn how to determine the pinout of these. I don't have a tranny tester, I don't have a test circuit, i don't have sockets, but i want to be sure they go in the right way 'round. And learn how to emperically test. I also assume that hooking them up backwards can ruin them.

selfdestroyer

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Re: Determining PNP collector and emitter
« Reply #1 on: February 25, 2016, 05:20:39 PM »
Im reading on this also.. This is helping me make sense of it
http://www.zen22142.zen.co.uk/ronj/cpt.html

Cody

Torgoslayer

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Re: Determining PNP collector and emitter
« Reply #2 on: February 25, 2016, 05:39:42 PM »
Thanks, i've read that trial and error method but i dont have a test circuit or breadboard. I can get the data with my multimeter, but i can't figure out how to interpret it. These oc42 all measure a slightly lower number on the pin nearest a painted-on dot, so i know they are trying to indicate a consistent pinout, but i can't figure out which reading indicates which pin it is. half the tutorials claim its always an emitter, and half say the opposite. stumped on who to believe on that particular aspect. Does higher reading on the diode test indicate E or C?!

lightsoundgeometry

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Re: Determining PNP collector and emitter
« Reply #3 on: February 26, 2016, 06:18:34 AM »

kgull

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Re: Determining PNP collector and emitter
« Reply #4 on: February 26, 2016, 06:49:09 AM »
The higher voltage drop is the emitter. The doping of the base-collector PN junction makes for a slightly lower voltage drop. This is pretty easy to test with most multimeters, that setting that we normally use as a continuity check usually will also measure the voltage drop across a diode.

Torgoslayer

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Re: Determining PNP collector and emitter
« Reply #5 on: February 26, 2016, 09:18:19 AM »
The higher voltage drop is the emitter. The doping of the base-collector PN junction makes for a slightly lower voltage drop. This is pretty easy to test with most multimeters, that setting that we normally use as a continuity check usually will also measure the voltage drop across a diode.
Thank you! That's the lesson I was looking for..I soldered them into a bumblebee/buzzaround and got the goodness. I'm so glad I asked, because I would have gone the other way around due to part markings and pcb marks. If anyone else runs into this, the oc42 has the collector marked with a dot. You are a rock star Kyle!