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Today, I started playing with transistors. I have here some teeny tiny 2n2222-108 transistors.

Actually, it didn't take long before I burned my finger against that transistor... It was really hot. I guess my mistake was to assume that a 680ohm resistance would be enough for the base.

Obviously I can't keep working like an idiot, otherwise it won't be long before something really bad happens.

But I have a problem here: I purchased these components from eBay, and except from the 2n2222-108, I have no way of identifying them to find a datasheet. Turns out that looking for "2n2222-108" on google yield me way too many results.

So, given that I only have "2n2222-108" as identifier, how can I know for sure the limits of the component?

Of course this question does not apply specifically to this component. I may be in the same case with any other.

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    \$\begingroup\$ The 2N2222 part should be specific. Otherwise, if you have a bunch, you can just test one. \$\endgroup\$ – Keelan Apr 23 '13 at 18:56
  • \$\begingroup\$ @Antoine_935 Welcome to EE.SE! It's recommended not to accept an answer to a question for at least a day or so, to stimulate discussion on the site and get more answers posted to the questions provided. \$\endgroup\$ – Adam Lawrence Apr 23 '13 at 21:39
  • \$\begingroup\$ Good piece of advise. Will do :) \$\endgroup\$ – Antoine_935 Apr 23 '13 at 22:39
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2n2222 is all you need to know. It is a standard kind of transistor made by many manufacturers. (In fact it is the single most common kind of transistor.) Go to one of the websites that does retail sales of electronic components (e.g., Jameco, Digikey, Mouser). Type "2n2222" into the search box. Click on the first transistor that comes up. Somewhere on that page will be a link that is labeled "data sheet". Click on it. You will get a pdf file (from some random manufacter) that lists the specs.

Here is the one (from ON Semi) that I got when I did this at Digikey just now.

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  • \$\begingroup\$ Thanks. Is there a difference between the 2n2222A and the one without "A"? These datasheets are quite daunting, I'll have to learn how to read that. For starters, how can I know the max current I can apply to the base? I didn't find it as-is in the sheet. \$\endgroup\$ – Antoine_935 Apr 23 '13 at 19:20
  • \$\begingroup\$ The "A" means that the max voltages are a little better. Here's a datasheet from Jameco that shows both jameco.com/Jameco/Products/ProdDS/38236MOT.pdf. By the way you'll often see "pn2222", which refers to a 2n2222 in a plastic package. (The original 2n2222 came in a package that looked like a little metal can.) \$\endgroup\$ – Wandering Logic Apr 23 '13 at 19:30
  • \$\begingroup\$ You shouldn't be worrying about the base current. The max current between collector and emitter is about 600mA to 800mA (depending on the data sheet you look at, so go with the lower value). The base current will be somewhere between 1/35th and 1/100th of the collector current (look at the "DC Current Gain" characteristics). But in any reasonable design you should be ignoring the base current and focusing on how the base/emitter voltage is controlling the collector/emitter current. \$\endgroup\$ – Wandering Logic Apr 23 '13 at 19:35

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