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I am thinking about ordering this:

http://www.ebay.com/itm/x100-Fairchild-PN2222A-2N2222A-NPN-Small-Signal-TO-92-Transistors-US-Seller-/171520659038?pt=LH_DefaultDomain_0&hash=item27ef6d8e5e

and I have no idea (Google has not proven helpful) what is the big difference between a 2n2222 and 2n2222a Transistor. I am using these for logic gates (for now just basic AND, NOT, and am working on my own full adder). I wish to buy the 100 pack on EBay, as it is cheap compared to buying a 15-pack at RadioShack (which only contains 5 of the kind I use) for a couple of bucks. What should I know, though, about 2n2222a and its use in logic gates (like different collector, emitter, base, etc.)?

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    \$\begingroup\$ What do the datasheets say? \$\endgroup\$ – Ignacio Vazquez-Abrams Feb 10 '15 at 3:27
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    \$\begingroup\$ Go to Digikey and buy 100 2N3904 for $11. It's another jellybean NPN. It looks like manufacturers are EOLing 2N2222s in non SMT packages, and that is making the remaining stock more expensive. Finally, do not buy electronic components on eBay. Ever. You don't know what you're getting, and more often than not they're fake. \$\endgroup\$ – Matt Young Feb 10 '15 at 3:35
  • \$\begingroup\$ Yeah, I had my thoughts about EBay. Main thing is, I just need a transistor that is perfectly (at most, just have to change which wire is which on a breadboard or so) compatible with 2N2222. I am looking up the 2N3904 now. \$\endgroup\$ – Cello Coder Feb 10 '15 at 3:38
  • \$\begingroup\$ digikey.com/scripts/DkSearch/… That the right one? 100 of them is about 11 dollars. They seem just what I need, based on what I have looked up. \$\endgroup\$ – Cello Coder Feb 10 '15 at 3:42
  • \$\begingroup\$ 2N3904BU is a Fairchild number. Really, for what you're doing any old small signal NPN will work. \$\endgroup\$ – Matt Young Feb 10 '15 at 3:51
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Both parts are about the same. The 2n2222A is a slight bit better in terms of Vceo, Vcbo, Vebo. But if you are not planning on stressing the part (higher voltages, etc) both will work well, especially for simple switching and logic circuits. The 2n2222 part is the older style part which might be the reason they are being offered at a low price.

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