2N2222A - pins are EBC or CBE?

[YurkshireLad]

I have a plastic TO-92 NPN transistor marked 2N2222A-1726. Searches for 2N2222A show datasheets for metal body transistors. P2N2222A show a TO-92, with pins from the front of CBE. I've seen references online to TO-92 2N2222A with pins of EBC. I found an old thread on these forums with a similar question (the site said "do you really want to reply to this old thread?) but it didn't really make it any clearer. How do I know exactly what I have and what the pins are?

The old thread is - https://www.eevblog.com/forum/beginners/identify-manufactor-for-simple-2n2222a/msg3671485/#msg3671485

[free_electron]

measure it ... some manufacturers use different pinouts... bc817 is another notorius one . same for bs170 and bs250 ...

[YurkshireLad]

Thanks. I will have to read how to measure it.

[bob91343]

Measuring is easy.  I suggest either of two methods.

1) An ohmmeter will show which pin is the base, as it will be the only pin that, when made positive, will conduct.
2) The cute little Chinese component tester will show you immediately what the pinout is.

You can also contact the manufacturer, if you know who they are.

[edavid]

The PN2222A EBC part was much more popular than the P2N2222A CBE part.

Normally I would say try EBC first, but considering the way your part is marked... who knows 

Do you have a DMM with an H_FE test function?  That should be good enough.

[Terry Bites]

I'm inclined to believe the ON Semi data sheet- they are one of the few (only) suppliers of the TO-92 packaged part.

https://www.google.co.uk/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&ved=2ahUKEwik0LS7raf2AhX6QUEAHe4SBagQFnoECAMQAQ&url=https%3A%2F%2Fwww.onsemi.com%2Fpdf%2Fdatasheet%2Fp2n2222a-d.pdf&usg=AOvVaw07YtuP6oWOLXEudI62AaUO

[themadhippy]

Do you have a DMM with an HFE test function?  That should be good enough.

Bog standard low  ohms range or diode /continuity range will do.

[YurkshireLad]

The PN2222A EBC part was much more popular than the P2N2222A CBE part.

Normally I would say try EBC first, but considering the way your part is marked... who knows 

Do you have a DMM with an H_FE test function?  That should be good enough.

I will check today. Thanks all.

[RoGeorge]

Typical BE reverse breakdown voltage is about 6V, while the BC breakdown voltage is much higher.  Based on this, you can do one of these:

- measure each junction resistance reverse polarized.  Depending on the DMM you have, you might be able to see the difference between BE and BC by measuring the resistance of each junction when reverse polarized, the BE has a smaller resistance than the BC when reverse polarized, but this might not work.

- measure the reverse voltage drop on each junction.  Put in series a 20-30V power supply, a 100 k\$\Omega\$ resistor, and the junction of the transistor as a diode reverse polarized.  Measure the voltage drop on the transistor junction while reverse polarized.  The reverse voltage on the BE should be much lower than the reverse voltage on BC.

- same as above, but use the internal voltmeter's resistance instead of the 100k limiting resistor.  Put the voltmeter in series with the reverse polarized junction and the source.  BE will only "take away" about 6V out of the total voltage, the rest will be to be seen on the voltmeter, while the CE will "take away" most of the volts so the DMM will should display close to nothing (or less volts anyways than when doing the same with the BE).

[macboy]

This is one case where the much loathed "Transistor tester" capability of a DMM comes in very handy. It takes only a few seconds to poke the device into the socket a few different ways until a sane hFE is displayed.

[edavid]

I'm inclined to believe the ON Semi data sheet- they are one of the few (only) suppliers of the TO-92 packaged part.

You are missing the point - there were (at least) 2 different TO-92 versions of the 2N2222A, with different part numbers and pinouts.  OP's part's marking doesn't match either part number.

PN2222A EBC https://www.onsemi.com/pdf/datasheet/pn2222a-d.pdf
P2N2222A CBE https://www.onsemi.com/pdf/datasheet/p2n2222a-d.pdf

[CaptDon]

If you don't know how to measure a transistor to figure out its basing what are you doing with the transistor in the first place? Nobody even mentioned the rare but existing ECB basing for rebranded 2N2222A parts shipped from the land of opiates and shitty fake electronic parts. It is anybody's guess these days.

[Ground_Loop]

The typically unhelpful reply not withstanding.  Do this:

1.  With a multimeter that has diode check connect the positive meter lead to any pin and the negative lead to one of the remaining. if you get a voltage reading somewhere between 0 VDC and 1 VDC (typically 0.5-0.7) the positive lead is on the base terminal.

2.  if no reading repeat 1. until you have identified the base terminal.

3.  With the base identified, move the negative lead to the third terminal.  A slightly higher voltage reading indicates the the negative lead is now on the emitter.  A slightly lower voltage reading indicates the negative lead is on the collector.

This procedure is for NPN transistors.  For PNP reverse the lead polarities.  If at any point you get a 0 VDC reading the device is shorted.

[TimFox]

Note that the plastic-case versions of this transistor are labeled PN2222A or P2N2222A.
The original nomenclature 2N2222A (JEDEC registration) should be reserved for the metal case part (TO-18 case).
Besides the pin order, the electrical specifications of the plastic versions differ from the JEDEC 2N2222A metal version.

[edavid]

3.  With the base identified, move the negative lead to the third terminal.  A slightly higher voltage reading indicates the the negative lead is now on the emitter.  A slightly lower voltage reading indicates the negative lead is on the collector.

For a PN2222, and a random cheap DMM in diode test mode, I found the difference was about 10mV (630mV vs 620mV).  You have to act fast since it drifts quickly as the part warms up.

[YurkshireLad]

The typically unhelpful reply not withstanding.  Do this:

1.  With a multimeter that has diode check connect the positive meter lead to any pin and the negative lead to one of the remaining. if you get a voltage reading somewhere between 0 VDC and 1 VDC (typically 0.5-0.7) the positive lead is on the base terminal.

2.  if no reading repeat 1. until you have identified the base terminal.

3.  With the base identified, move the negative lead to the third terminal.  A slightly higher voltage reading indicates the the negative lead is now on the emitter.  A slightly lower voltage reading indicates the negative lead is on the collector.

This procedure if for NPN transistors.  For PNP reverse the lead polarities.  If at any point you get a 0 VDC reading the device is shorted.

It may be EBC. For step 3, I get 0.72v with the negative on the first pin, and 0.72v with the negative on the third pin, though it drops to 0.71v after a second or so.

Thanks

[fourfathom]

I think H_FE or base-emitter reverse breakdown are the better ways to determine pinout.  The forward-biased B-E and B-C junction voltages are just too close.

[TimFox]

Base-emitter breakdown should be a definitive test, but be careful not to run much current for a long time in that condition, since it will result in degradation in h_FE and noise.
Almost all silicon transistors have a B-E breakdown between 5 and 7 V, but the C-B breakdown is usually above 20 V.  ON rates the P2N2222A for minimum 70 V for V_CBO breakdown (emitter open), but 6 V for V_EBO (collector open).
This article  https://downloads.hindawi.com/journals/apec/2001/053209.pdf  specifically tested 2N2222As.

[Ground_Loop]

I think H_FE or base-emitter reverse breakdown are the better ways to determine pinout.  The forward-biased B-E and B-C junction voltages are just too close.

Agree this is more definitive, but forward voltage drop can be done with minimal equipment and connections.

[TimFox]

As shown above, the forward voltages of the two PN junctions in an NPN transistor cannot be differentiated reliably.  The breakdown voltages are very different.

[David Hess]

I just did some testing and had no problem distinguishing the emitter from the collector by the emitter's slightly higher voltage drop.  It may be only 5 millivolts, but the readings were always stable.

A reverse breakdown test risks damaging some transistors, and some rare transistors have a high base-emitter breakdown anyway.

[YurkshireLad]

My DMM is too cheap and inaccurate. 

[TimFox]

I just did some testing and had no problem distinguishing the emitter from the collector by the emitter's slightly higher voltage drop.  It may be only 5 millivolts, but the readings were always stable.

A reverse breakdown test risks damaging some transistors, and some rare transistors have a high base-emitter breakdown anyway.

If the difference between forward-bias voltages is only 5 mV out of 600 to 700 mV, how do you know which one is which?  Certainly not by the datasheet.

[bob91343]

Just measure the breakdown voltage.  Or rather, connect the junction in reverse polarity to a power supply via a series resistor of, say, 10,000 Ohms and measure the current.  Raise the voltage on each junction until you start to see some current.  When the voltage gets to 10 Volts, the base-emitter should draw about 50 microamperes.  The base-collector junction very much less, essentially zero.

[magic]

Or build the hFE test circuit used in cheap DMMs.

It assumes 0.7V base voltage, sends ~10µA to the base and measures the resulting collector/emitter current.
Not super accurate, but you will easily see a difference if you insert the transistor backwards.

Another simple solution: smash it with a hammer; the terminal connected with a big metal plate behind the front face of the package is was the collector.