2N2222A - pins are EBC or CBE? - Page 1
Forum section: electronics / beginners

author: YurkshireLad
author_rank: Frequent Contributor
timestamp: March 02, 2022, 12:52:57 am
content: 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

author: free_electron
author_rank: Super Contributor
timestamp: March 02, 2022, 01:09:06 am
content: measure it ... some manufacturers use different pinouts... bc817 is another notorius one . same for bs170 and bs250 ...

author: YurkshireLad
author_rank: Frequent Contributor
timestamp: March 02, 2022, 01:16:38 am
content: Thanks. I will have to read how to measure it.

author: bob91343
author_rank: Super Contributor
timestamp: March 02, 2022, 02:02:41 am
content: 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.

author: edavid
author_rank: Super Contributor
timestamp: March 02, 2022, 02:48:50 am
content: 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 knowsDo you have a DMM with an HFEtest function? That should be good enough.

author: Terry Bites
author_rank: Super Contributor
timestamp: March 02, 2022, 11:56:04 am
content: 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

author: themadhippy
author_rank: Super Contributor
timestamp: March 02, 2022, 12:40:58 pm
content: QuoteBog standard low ohms range or diode /continuity range will do.

author: YurkshireLad
author_rank: Frequent Contributor
timestamp: March 02, 2022, 01:14:44 pm
content: Quote from: edavid on March 02, 2022, 02:48:50 amI will check today. Thanks all.

author: RoGeorge
author_rank: Super Contributor
timestamp: March 02, 2022, 01:39:36 pm
content: 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).

author: macboy
author_rank: Super Contributor
timestamp: March 02, 2022, 02:19:19 pm
content: 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.

author: edavid
author_rank: Super Contributor
timestamp: March 02, 2022, 03:17:50 pm
content: Quote from: Terry Bites on March 02, 2022, 11:56:04 amYou 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 EBChttps://www.onsemi.com/pdf/datasheet/pn2222a-d.pdfP2N2222A CBEhttps://www.onsemi.com/pdf/datasheet/p2n2222a-d.pdf

author: CaptDon
author_rank: Super Contributor
timestamp: March 02, 2022, 03:41:55 pm
content: 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.

author: Ground_Loop
author_rank: Frequent Contributor
timestamp: March 02, 2022, 05:35:37 pm
content: 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.

author: TimFox
author_rank: Super Contributor
timestamp: March 02, 2022, 05:37:52 pm
content: 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.

author: edavid
author_rank: Super Contributor
timestamp: March 02, 2022, 05:55:16 pm
content: Quote from: Ground_Loop on March 02, 2022, 05:35:37 pmFor 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.

author: YurkshireLad
author_rank: Frequent Contributor
timestamp: March 02, 2022, 07:42:22 pm
content: Quote from: Ground_Loop on March 02, 2022, 05:35:37 pmIt 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

author: fourfathom
author_rank: Super Contributor
timestamp: March 02, 2022, 08:24:13 pm
content: I think HFEor 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.

author: TimFox
author_rank: Super Contributor
timestamp: March 02, 2022, 08:57:34 pm
content: 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 inhFEand 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 forVCBObreakdown (emitter open), but 6 V forVEBO(collector open).This articlehttps://downloads.hindawi.com/journals/apec/2001/053209.pdfspecifically tested 2N2222As.

author: Ground_Loop
author_rank: Frequent Contributor
timestamp: March 02, 2022, 10:47:48 pm
content: Quote from: fourfathom on March 02, 2022, 08:24:13 pmAgree this is more definitive, but forward voltage drop can be done with minimal equipment and connections.

author: TimFox
author_rank: Super Contributor
timestamp: March 02, 2022, 11:49:47 pm
content: 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.

author: David Hess
author_rank: Super Contributor
timestamp: March 03, 2022, 02:19:57 am
content: 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.

author: YurkshireLad
author_rank: Frequent Contributor
timestamp: March 03, 2022, 02:45:25 am
content: My DMM is too cheap and inaccurate.

author: TimFox
author_rank: Super Contributor
timestamp: March 03, 2022, 03:51:04 am
content: Quote from: David Hess on March 03, 2022, 02:19:57 amIf 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.

author: bob91343
author_rank: Super Contributor
timestamp: March 03, 2022, 05:16:22 am
content: 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.

author: magic
author_rank: Super Contributor
timestamp: March 03, 2022, 06:30:47 am
content: 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 packageiswas the collector.

author: CaptDon
author_rank: Super Contributor
timestamp: March 03, 2022, 02:46:30 pm
content: To the O.P., Many digital multimeters today use a somewhat standard method to measure things using the DIODE position. It is often a constant current source set to 1 milliamp. The current alone is deemed insufficient to damage solid state devices. Typical diodes will read something between .625 to .685 (or maybe 625 to 685 depending on your meter) and that is the actual measured voltage drop across the junction when forward biased. When reverse biased it will generally read like an open circuit although old germanium transistors often show a lot of leakage. Some transistors have internal diodes that may throw you off. Mosfets often have a body diode from S to D and that will throw you off unless you expect it. As you are testing mosfets they may appear shorted S to D if there is a residual gate charge remaining. Be aware that good meters limit the open circuit test voltage to 1vdc up to maybe 1.5vdc, this will not harm 99.99% of solid state devices. There are SOME meters that use as much as 9vdc and I have one that is 22vdc. This will destroy many fets and mosfets by breaking down the sensitive gate layer so be careful and know your meters O.C.V.!! As other posters have stated the forward biased E/B junction will tend to be a few millivolts higher than the B/C junction. It varies with design. I have good transistors with identical readings, although generally 'identical readings' indicate a transistor with some sort of failure mode present, usually shorted E to C or very high leakage and low gain. Meters with 1vdc O.C.V. won't test LED's very well. Cheers!!

author: TimFox
author_rank: Super Contributor
timestamp: March 03, 2022, 02:54:22 pm
content: A simple test using not much more than a DMM:First, using either the diode mode or a resistance mode, identify the two PN diodes in the NPN structure and their forward direction.Then, use a 9 V battery in series with, say, 40 k ohms (anywhere from 30 to 50 would do).Connect that to the 10 megohm input of the DMM in voltage mode, and you will measure close to 9 V.Connect that to each of these diodes:If you measure < 1 V, you are in the forward direction and should reverse the connections to the diode.If you measure close to 9 V, you have found the C-B diode, whose breakdown voltage should be larger than 9 V.If you measure between 5 and 7 V, you have found the B-E diode, and are applying between 100 uA and 50 uA (with 40 k)--disconnect quickly.Really old germanium transistors had BE breakdown voltages comparable to the CB breakdown, but virtually all planar silicon transistors have this low breakdown voltage as a feature.

author: Zero999
author_rank: Super Contributor
timestamp: March 06, 2022, 06:41:54 pm
content: If the diode check is inconclusive. I recommend the hFEtest, over breakdown voltage, because it doesn't damage the transistor and a much lower voltage is more convenient. All that's needed is a resistor 10k to 1M and a 1V to 5V power supply. Connect the base to the collector/emitter via the resistor, with the power between the collector and emitter and measure the current draw. The circuit will pull the most current, when the resistor is connected between the base and collector and the emitter is negative. Don't leave it connected for too long, as the hFEincreases with temperature which means the transistor can get too hot. It's better to start with lower voltages/higher value resistors.

author: RoGeorge
author_rank: Super Contributor
timestamp: March 06, 2022, 07:38:04 pm
content: Quote from: Zero999 on March 06, 2022, 06:41:54 pmThat would make a very clean distinction (in case measuring Vbe and Vbc doesn't).I didn't try, but instead of a 3V power supply those 3V could be as well coming from the DMM set on measuring diodes. Q1 will show open, and Q2 about 1V (on the DMM set on diodes range).

author: David Hess
author_rank: Super Contributor
timestamp: March 06, 2022, 11:16:23 pm
content: Quote from: TimFox on March 03, 2022, 03:51:04 amI tested a bunch where I already knew the pinout, and the emitter junctions all had higher voltage drop than the collector junctions.