How do you tell PNP from NPN

[multi-volti at MULTI-VOLTI.COM]

The base is only the middle lead on certain transistors. On many it's at one
end. Depends on the geometry of the transistor die (chip inside the
package).

You can check with your ohmmeter all three combinations of pairs (use a
known good device for which you know it's 'gender'...NPN or PNP, and note
which polarity is what with your ohmmeter. You can then use this as your
reference in the future...PNP will have opposite conduction orientation for
ohmmeter leads than NPN.

Many DMM's (notoriously Radio Shack in the 1980's and I don't remember who
else's) had the red lead as negative for ohms (by + or - for ohms I mean the
applied test voltage polarity).

Another test is a diode...if your black lead goes to the cathode (bar) and
the red goes to the anode (non-bar-end) and the diode conducts, your
ohmmeter was responsibly designed. If not, I suggest you throw brand loyalty
out the window on your next purchase.

I HOPE I HOPE I HOPE any manufacturer that has a diode scale that apparently
gives diode junction voltage has proper polarity!

Murray


----- Original Message -----
From: "Dan Pividal N4VET" <OTAKEBI at AOL.COM>
To: <HEATH at LISTSERV.TEMPE.GOV>
Sent: Thursday, February 13, 2003 5:06 PM
Subject: How do you tell PNP from NPN


> Do any of you know a sure fire way to tell if a transistor is NPN or PNP?
> I know the base is the middle lead and that if I hold the flat part of the
> transistor toward me with the leads down that should put the emitter to
the
> far left.
> But, that is not the case with all transistors.
> Can anyone help?
> Thanks,
> Dan
>
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