> Hello,
>=20
> I have a few 2N2222A in TO-18 metal can package as pictured below:
>=20
> http://i.imgur.com/UYKAuyD.jpg
> http://i.imgur.com/F5AzBtL.jpg
>=20
> Are these germanium or silicon?

Definitely Silicon.=20

>=20
> What would be the advantage of using the TO-18 package over TO-92
> package?

When they were originally designed there was no TO-92 package, the TO-18 wa=
s the smallest package around for consumer stuff. There are versions of thi=
s transistor around now in TO-92 (look for part number PN2222A) and surface=
 mount (MMBT2222A from On Semi, among others).

> What is the approximate value of that transistor in TO-18 package (ST Bra=
nd)?

Very cheap, they are what gets termed a 'jelly bean' component in that they=
 are rugged, have decent current capability for a small transistor (e.g. fo=
r driving lamps and relays), and a collector voltage rating that is high en=
ough for driving relays when appropriate protection is used against inducti=
ve spikes.

Military rated versions cost about GBP =A311, the ones you have should be a=
bout 10 cents.

Found these ones at Farnell in the UK ...

http://onecall.farnell.com/_/2n2222/transistor-npn-to-18/dp/SC06697 for a T=
O-18

http://onecall.farnell.com/on-semiconductor/p2n2222ag/transistor-npn-to-92/=
dp/SC12549 for a TO-92

http://onecall.farnell.com/semelab/2n2222acsm/transistor-hirel-npn-40v-0-6a=
-lcc1/dp/1856798 for a Hi-Rel version (but no indication of screening optio=
n, so don't expect JANTXV or JANS versions).

http://onecall.farnell.com/fairchild-semiconductor/mmbt2222/transistor-npn-=
30v-0-6a-sot23/dp/1467896 for an SOT-23 version.

A myriad more from this search page ...
http://onecall.farnell.com/jsp/search/browse.jsp?N=3D411+2032+204244&Ntk=3D=
gensearch&Ntt=3D2222&Ntx=3Dmode+matchallpartial&No=3D0&getResults=3Dtrue&ap=
pliedparametrics=3Dtrue&locale=3Den_GB&divisionLocale=3Den_GB&catalogId=3D&=
skipManufacturer=3Dfalse&skipParametricAttributeId=3D&prevNValues=3D411+203=
2+204244&filtersHidden=3Dfalse&appliedHidden=3Dfalse&autoApply=3Dfalse&orig=
inalQueryURL=3D%2Fjsp%2Fsearch%2Fbrowse.jsp%3FN%3D411%2B2032%2B204244%26Ntk=
%3Dgensearch%26Ntt%3D2222%26Ntx%3Dmode%2Bmatchallpartial%26No%3D0%26getResu=
lts%3Dtrue%26appliedparametrics%3Dtrue%26locale%3Den_GB%26divisionLocale%3D=
en_GB%26catalogId%3D%26skipManufacturer%3Dfalse%26skipParametricAttributeId=
%3D%26prevNValues%3D411%2B2032%2B204244







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