Re: [CAD_CAM_EDM_DRO] OT Transistors

John wrote:

> Okay my patience is wearing beyond thin with this [real bad language]
> circuit I'm 'making'. If I'm looking at a transistor it has one curvey
> rounded side and one flat side. If I turn it so the flat side is facing me
> the collector is the far right pin isn't it? And Q1, or the emittor, is the
> far left?
>
> Please help me before I go mad and start chewing limbs off,
>

The most standard arrangement, with flat toward you and leads down,
is E B C reading from left to right. But, ALL possible combinations have been
used on various transistors. It is actually possible, with any Ohmmeter
that applies over 1 volt to the component under test, to find out the
correct pins. The trick is that bipolar transistors are fairly symmetrical
when read only one junction at a time (which can tell you NPN from
PNP). But, the gain is not symmetrical, current from base to emitter
causes much greater current through the collector. Base can be found
as it will conduct to both E and C (with the right polarity). Then, connect
the meter between E and C. For an NPN, you'd want the positive lead
to the collector. Apply a 1 Meg Ohm resistor (you may have
to try different resistor values depending on the gain of the transistor)
from collector to base. If your guess of the E and C is correct, you
will see a meter reading FAR below the 1 Meg Ohm, maybe 10 K Ohm
or so (indicating gain of about 100 there). If your guess is wrong,
the transistor will have minimal gain backwards, and you can switch
the meter leads and try again.

Also, watch out for FETs and Darlington transistors, which will confuse
you. If you find no gain either way, you may have a JFET.

Jon