2N2222 burning notes

2N2222 burning out in the lab at 22 V

Ask Question

Asked 11 days ago

Modified today

Viewed 2k times


According to the datasheet, a 2N2222 can handle VCE(max)VCE(max) up to 40 V40 V. However, in the lab, I’ve seen different 2N2222s fail (get turned on) and burn with the below circuit. I need to know why this happens.

My transistor starts burning after turning on the power supply. As I checked the transistor, it works fine up to 15 V15 V as VCC, but after that, the transistor gets turned on, and it starts burning at 22 V22 V. I bought my transistor from markets in Shenzhen. The full label is 2N2222A.

I just connected the RBRB to the ground to ensure that the transistor is off.

24V 2N2222 circuit



edited Nov 8 at 10:44

Nick Bolton's user avatar

Nick Bolton

1,56266 silver badges2727 bronze badges

asked Nov 3 at 9:20

John Jin's user avatar

John Jin

39911 silver badge1111 bronze badges

  • 2You need to provide more details like PCB layout, full schematic, photographs, power supply type and surge resilience, anti-static precautions in place and used etc.. – Andy aka Nov 3 at 9:49
  • 1I appreciate your comment. I just assembled them on the breadboard, and the power supply is a variable linear 0-30 volt 3A power supply(MEGATEK-MP-3003). – John Jin Nov 3 at 10:19
  • 3Immediately fail, or fail after a specific period or number of operations? Is that a switch on the transistor base? – HandyHowie Nov 3 at 11:09
  • 3(1) Are your 2N2222 actually 2N2222A, from eBay or DigiKey? (2) Why Rb connected to ground? (3) Do you have any project/testing spec? – tlfong01 Nov 3 at 11:35  
  • 1I appreciate all your comments. My transistor starts burning after turning on the power supply. As I checked the transistor, it works fine up to 15 as VCC, but after that, the transistor gets turned on, and it starts burning at 22V. I bought my transistor from markets in Shenzhen. The full label is “2N2222A.”. I just connected the Rb to the ground to ensure that the transistor is off. – John Jin Nov 4 at 4:06
  • 1Does the label list a manufacturer? – mkeith Nov 5 at 17:12
  • 1@tlfong01 “from eBay or DigiKey?” Err, that’s like saying “only trust parts either found on some junkyard or by the well-known vendor Digikey”. Don’t buy electronic components from Ebay, Aliexpress and similar scammer communities. – Lundin Nov 8 at 15:50
  • @Lundin: Well, I very seldom buy from eBay, never from Digidkey. I usually buy from TaoBao (AliExpress), and sometimes from Element14 (Farnell) – tlfong01 Nov 9 at 6:07  
  • 2Just now I searched my junk box and found some 500 pieces of TaoBao no brand 2N2222. Perhaps I would do some destructive testing. imgur.com/a/qreXS1q – tlfong01 Nov 9 at 6:20  
  • 2Before testing, I am googling a datasheet: P2N2222A Amplifier Transistors NPN Silicon datasheet – OnSemi 2003jan onsemi.com/pdf/datasheet/p2n2222a-d.pdf – tlfong01 Nov 9 at 6:29  
  • 4I also googled Wikipedia for the pin order difference: 2N2222 Wikipedia en.wikipedia.org/wiki/2N2222 Note: Replacements for the 2N2222 are commonly available in the cheaper TO-92 packaging, where it is known as the PN2222 or P2N2222, which has similar specifications except for the lower maximum collector current. The P2N2222 has a different order of pins than the metal case 2N2222 imgur.com/a/NWzig8i, with its emitter and collector connections switched; other plastic-case transistors also have different pinouts. – tlfong01 Nov 9 at 7:32   
  • 1@tlfong01 Well yeah someone already posted an answer below saying as much. – Lundin Nov 9 at 7:57
  • @Ludin: Yes, I know there are already 5+ answers. I am just trying to confirm/and or complement those answers. – tlfong01 Nov 9 at 8:18  
  • 1Now I have set up a bread board rig for testing ten 2N2222 at the same time: imgur.com/a/NmHEZMY. My cheapy DMM measured Hfe in the range of 150~300. – tlfong01 Nov 10 at 3:40  
  • 2And I have set up my digital DC storage PSU Riden RD6000 with 24VDC and 100mA to test the 2N2222 switching on/off a LED: imgur.com/a/Dze9zYa. – tlfong01 Nov 10 at 14:44   
  • 2Now I am using Electronics Tutorials as a reference to my 2N2222 as switch testingimgur.com/a/ps8VQBh – tlfong01 Nov 11 at 3:48  
  • 1A coupled of year ago I read a similar Q&A where this mismatch of pinout has a reason and therefore not seen as a mistake. Just now I googled further and found another similar post giving a different reason: (1) BJT in Reverse Active Mode of Operation – Asked 10 years ago, Viewed 25k times electronics.stackexchange.com/questions/29756/… (2) 2N2222A Mismatch between emitter and collector – EESE, Asked 8 years ago, viewed 19k times electronics.stackexchange.com/questions/109391/…. – tlfong01 Nov 11 at 14:05  
  • 1Similarly for MMBT2222, there are also two different pin out orders: Style 6 and Style 7: imgur.com/a/RFvIyal – tlfong01 2 days ago  
  • 1Now I am doing more testings: (1) I use my cheapy DMM DT-9205A to measure the hFE of 4 TO92 2N2222 A331 samples. I found the hFE measurements are 258~276 for ebc, and 16~18 for cbe. Perhaps I should also measure the Vce(sat) and verify that that cbe samples have very small Vce(sat). – tlfong01 2 days ago  
  • 1I also searhed my old text files and found the following about 2n2222 pinouts by @Sredni Vashtar: tlfong, my opinion is that the pn2n2222 was created for the Japanese market (I have no hard evidence, though) where transistors have usually the CBE pinout, opposite to the customary (but not universally shared) EBC pinout of American and European transistors (I am talking about small signal BJTs – power transistor are another thing and the usually have to middle pin connected to the collector or drain). – Sredni Vashtar Oct 5, 2020 at 16:59 – tlfong01 yesterday   
  • 1us_eu_jp_bjt_to92_pinouts: imgur.com/a/Cv5ClvG – tlfong01 yesterday  
  • 1Transistor Marking Codes – Csaba Gajdos, YO5OFH, 2011jul29 qsl.net/yo5ofh/doc/transistor_codes.htm – tlfong01 yesterday  
  • 1Difference between bc547 and 2n2222 – Asked 5 years ago Viewed 34k times electronics.stackexchange.com/questions/276881/… The basic difference is the 2N2222A is explicitly labeled “switching mode transistor”, which explains the much higher collector current in the same casing. One has to expect bad linearity and high output capacitance from that. – Janka Dec 26, 2016 at 9:33 2N2222, 2N2222A Datasheet and Application Notes – HomemadeCircuits, 2020dec30 homemade-circuits.com/how-to-understand-transistor-2n2222 – tlfong01 yesterday  
  • 1@tlfong01 Stack Exchange comments are considered temporary and can disappear at any moment without warning. This all looks like helpful stuff! You might consider including it in a supplementary answer post. – uhoh 23 hours ago
  • 1@uhoh: Many thanks for your advice. So I will try to write up a supplementary answer post. Cheers. – tlfong01 20 hours ago  
  • 1Now I have some 100 pieces of ST 2N2222A metal can samples in hand, with hFE in the range 160~200. So I would repeat the OP’s experiments and see if they can stand 22V Vce. imgur.com/a/nX2Rc7I. I got them from ShenZhen, but they have sharp and clear marking of “ST logo and 2N2222A M1217 Malaysia” The TaoBao shop selling it is a 7 year old shop with “5 Dimond” ranking. They sell 2222A and 2907A, both for ¥1.20/pcs. – tlfong01 17 hours ago   
  • 1/ to continue in supplementary answer below, … – tlfong01 5 hours ago  

Add a comment

Start a bounty

6 Answers

Sorted by:                                              Highest score (default)                                                                   Date modified (newest first)                                                                   Date created (oldest first)                              


The only possible answer is: you don’t have that circuit.

So one of the following must be true:

  1. Your transistor isn’t actually 2N2222,
  2. Your circuit is not wired as you think,
  3. Your voltage isn’t 22 V,
  4. You have something (unsuitable) connected at output,
  5. Faulty test equipment is leading you completely astray.

Obviously the easiest things to check are the wiring, the resistor values, and the voltage. Comments have made the suggestion that you have a counterfeit part — certainly a possibility. Also of course if the test equipment is faulty, Vout could be something else. If you’re getting surprising results: always check the test equipment. In this particular case, given that the transistor is burning up, it’s pretty evident something is very wrong.

The first thing to check is the pinout, both from datasheet for the exact part number, and by confirming on the actual device.

Variant Pinout

Another possibility is that your transistor has a different pinout than you’re expecting, such as the P-variant:

From Wikipedia

Which would mean you actually have the following, which has VEB of 22 V, where the limit is 6 V (see datasheet portion below).


simulate this circuit – Schematic created using CircuitLab

Identifying Pins

The classic method for identifying the pins of an out-of-circuit NPN transistor is to measure the voltage drop with the diode-mode of a multimeter. You expect approximately 0.6 V measuring from B to C and from B to E, and OL in all the other pairings. The one with the slightly larger drop is the emitter. The 2N3904 I just measured gave 0.664 V and 0.684 V. (Sorry, no 2N2222 to hand.)

I recommend you try this on your parts which are burning up and see if you can confirm the pinout.

Datasheet Fragment

 From datasheet



edited Nov 8 at 14:25

answered Nov 3 at 10:30

jonathanjo's user avatar


6,5171616 silver badges4444 bronze badges

  • 5That evil PN2222 was what came to my mind as well. – Janka Nov 3 at 13:50
  • 1This is why I always physically test the pinout even when I think I know which one it is. – Ian Bland Nov 3 at 17:52
  • 1@IanBland Good suggestion, I added a section on that. – jonathanjo Nov 3 at 18:56
  • 2Dear Jonathanjo, thank you very much for your answer. I will recheck the transistor to assure myself about the circuit behavior. I think that my transistor is a counterfeit part, but I will check your answer step by step and let you know. – John Jin Nov 4 at 4:11

Add a comment


One possible explanation: the 2N2222 is most famous for having two different pinouts, as shown in this Wikipedia article.

As a result, it’s often connected with emitter and collector reversed, and in such a configuration the base emitter junction can easily become reverse biased beyond its reverse breakdown voltage (which is only 10V or so).

That junction conducts well, and quickly overheats. The transistor is toast before you even realise you bought one of the upside-down versions.



answered Nov 3 at 13:46

Simon Fitch's user avatar

Simon Fitch

11.6k88 silver badges4545 bronze badges

  • If I’m not mistaken, reverse browndown minimum is given as 6V. Do you know if the transistor is likely to fail with CE open? BE open? – jonathanjo Nov 4 at 7:40
  • 1This wouldn’t happen with BE open, since that’s the junction conducting and heating in this scenario. It could still happen with C disconnected altogether. The lower the reverse breakdown voltage, the less power is dissipated per amp, and the less likely damage is, but I think 6V is atypical. Most devices will break down at around 9V, as far as I know, but I haven’t measured any to know what the distribution is. – Simon Fitch Nov 4 at 12:46

Add a comment


According to the datasheet, a 2N2222 can handle VCE(max) up to 40 V. However, in the lab, I’ve seen different 2N2222s fail (get turned on) and burn with this circuit

the power supply is a variable linear 0-30 volt 3A power supply (MEGATEK-MP-3003)

My transistor starts burning after turning on the power supply

One possibility then is that the power supply is pushing way more than 40V into that transistor as it is turned on.

Use a digital oscilloscope to capture the transient that occurs then the power supply is turned on using the power switch. Some poorly designed supplies wildly overshoot the output voltage when the mains power is turned on.

This will be the culprit, assuming that:

  1. The transistor is not fake and actually meets its specifications.
  2. The transistor actually has the pinout you think it does. Check it with the diode function on a multimeter!
  3. Verify that the emitter and collector are where you think they should be by measuring the current gain when the transistor is on. Use a the following circuit:

simulate this circuit – Schematic created using CircuitLab

  1. The circuit, wired as shown in the question, is checked with voltage measurements with a multimeter when supplying say 12V to the circuit. Base to emitter should be 0V. Collector to emitter should be 12V. The voltage across the collector resistor should be 0.000V.

To completely eliminate the power supply as the potential source of trouble, use 9V batteries in series as a power source instead. You can use crocodile jumpers to connect them in series. 9×4=36V – the transistor should handle that without a problem.

I have assembled your circuit using known-good 2N2222 transistors and nothing happens when the power is turned on: the transistor remains off.



edited Nov 4 at 23:50

answered Nov 4 at 20:52

Kuba hasn't forgotten Monica's user avatar

Kuba hasn’t forgotten Monica

20.3k11 gold badge3030 silver badges6868 bronze badges

Add a comment


As I checked the transistor, it works fine up to 15 as VCC, but after that, the transistor gets turned on, and it starts burning at 22V.

I made simulations and some measurements with a real 2N2222 transistor.

Then let’s see what happens at 15 V VCC voltage. If we do not connect the collector, it will be an 8.8 V Zener diode. By connecting the collector, it becomes a reverse-biased transistor, but it can handle the 25 mA collector current indefinitely (250 mW). It’s getting a little warm. 

At a supply voltage of 24 V, the Zener current increases to 12.5 mA, but this does not destroy the transistor. It works continuously and gets a little warm. When we connect the collector here, the transistor still works, only the higher collector current heats up the transistor very quickly. It will last a few seconds until we can measure currents. If it is turned off in time, the transistor remains functional. After about 10 seconds it overheats and breaks down (700 mW). 

The actual measured values were: UB = 980 mV, IC = 86 mA.

I sometimes use reverse biased base-emitter junction as a low capacitance 9 V Zener if I need one. (For the simulation, I modified the transistor, connected a diode and a Zener between the base and emitter.)



edited Nov 10 at 8:19

answered Nov 4 at 20:00

csabahu's user avatar


2,05133 silver badges55 bronze badges

Add a comment


Nobody has asked you what kind of load you are switching, although since it isn’t shown, it is another aspect of the diagram not representing the actual circuit you are operating.

If you are switching an inductive load, when you turn off the transistor, the current in the inductor cannot immediately change. Since the switch is now high impedance, the current which the inductor is trying to maintain can create a very high voltage at the collector of the transistor, leading to breakdown and eventually “burning” the transistor. For example if the load is the coil of a small signaling relay, it’s possible for the collector to see 700 V700 V or more at the peak of the inductive “kickback”

The solution is to place a snubber diode from the collector to V+ oriented with the cathode at the collector, so that any voltage higher than V+ present on the collector will be conducted to the V+ supply. This will take the energy stored in the inductor and return it to your power rail instead of dissipating it through the transistor.

If your load is resistive or capacitive, this would not apply.



edited Nov 8 at 14:22

Nick Bolton's user avatar

Nick Bolton

1,56266 silver badges2727 bronze badges

answered Nov 3 at 20:21

David Savory's user avatar

David Savory

4122 bronze badges

  • 3Dear David, Thank you very much for your explanation. My load is a simple resistor, as I mentioned in the main question. – John Jin Nov 4 at 4:21
  • 3The OP showed the circuit in the question. There is no reason the transistor should be turning on at all since the base is pulled low with a 1 k resistor. – mkeith Nov 5 at 17:16

Add a comment


/ continued from comments above, …

/ Update 2022nov15hkt1542, …

  1. Fiarchild MMBT2222A datasheet sayds that for pulse or low duty cycle operation, the absolute maximum value would be different from the spec. So I will be using PWM signal with different frequency and duty cycle to verify that. I will be using the manual/uart controlled XY-PWM sig gen as the test signal.

How can Rpi4B python UART talk to XY PWM Signal Generators? Asked 3 years ago Modified 3 years ago Viewed 1k times

xy-pwm sig gen

  1. I will also try the FairChild SOT23 MMBT2222A.

  1. How can I use a 2N2222 transistor as a temperature sensor? Asked 2 years, 1 month ago Modified 2 years, 1 month ago Viewed 6k times

Now I am thinking of monitoring the temperature rise of the 2N2222 in “wrong” pinout/configuration, and increasing the Vce voltage from 5V to 24V, and see if the 2N2222 is buring out, as reported by the OP.

  1. I am going to test the Malaysia STMicroelectronics 2N2222A below.
enter image description here

temp sensor
enter image description here
enter image description here



edited 2 mins ago

answered 4 hours ago

tlfong01's user avatar


2,71111 gold badge88 silver badges1717 bronze badges

Add a comment

Categories: Uncategorized

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

This site uses Akismet to reduce spam. Learn how your comment data is processed.