W
Watson A.Name - 'Watt Sun
Guest
I printed out the data sheets for some common BJTS, BC547-8-9, BC237-
8-9, 2N3904, and a couple more (mainly PNP). I laid the sheets out
and compared the specs and graphs and I found that the differences
aren't that great, and in some cases it seems to be more of
terminology than the actual values. For comparison purposes I used
the Fairchild data sheets since I find them to usually be the cheapest
and easy to get. Also, if you do a google search for these, the
Fairchild data sheets will be one of the first to pop up.
I first compared the BC547 and BC237, and they're quite similar. The
graph pages look identical. I made the mistake of printing double
sided, so I can't hold them up to the light and see if they're
identical, but they certainly look to be. The specs are very similar,
just minor diffs.
I compared the 2N3904 and BC547 and I found that the values might have
differences that are more influenced by the test, like current and
voltage for the Ft. In the case of the 2N3904, Tr, Tf, etc., are
given but the BC547 had no specs at all for those. And that is
despite the heading for the BC547 that says they're for switching
applications.
The cases for all these transistors is the T0-92, which is identical
in size. The 2N3904 has the standard JEDEC pinout of E B C, whereas
the BCs have it reversed, C B E. The BCs have beta ranges so you can
get a BC237A, B, or C. If you want to change the gain range for the
2N3904, sorry, that's all you get, other than going to the lower gain
2N3903.
I was looking at the EPE mag of a month or two ago (Barnes and Noble
has 'em, but they're always a month or two late). I found that some
projects used the BCs in one place and the 2Ns in another. Why, I
haven't a clue. I would just forget the 2Ns and go with the BC327 and
BC337 for higher current. Here, the Fairchild 2N3904 is 9 cents each,
and the Gen Semi BC547 is 8 cents each. For some odd reason,
Fairchild's BC547 is a much higher 21 cents. But there seems to be no
significant advantage of one over the other.
Maybe if I get some time, I'll make a table with columns for the
different BJTs and rows for the specifications, so they will be side-
by-side for easy comparison. But one data sheet may use Vbr(cbo) and
another may use BV(cbo). Obviously the same, but I can't remember
which is the standard.
Anyway, it's been interesting and enlightening..
--
@@F@r@o@m@@O@r@a@n@g@e@@C@o@u@n@t@y@,@@C@a@l@,@@w@h@e@r@e@@
###Got a Question about ELECTRONICS? Check HERE First:###
http://users.pandora.be/educypedia/electronics/databank.htm
My email address is whitelisted. *All* email sent to it
goes directly to the trash unless you add NOSPAM in the
Subject: line with other stuff. alondra101 <at> hotmail.com
Don't be ripped off by the big book dealers. Go to the URL
that will give you a choice and save you money(up to half).
http://www.everybookstore.com You'll be glad you did!
Just when you thought you had all this figured out, the gov't
changed it: http://physics.nist.gov/cuu/Units/binary.html
@@t@h@e@@a@f@f@l@u@e@n@t@@m@e@e@t@@t@h@e@@E@f@f@l@u@e@n@t@@
8-9, 2N3904, and a couple more (mainly PNP). I laid the sheets out
and compared the specs and graphs and I found that the differences
aren't that great, and in some cases it seems to be more of
terminology than the actual values. For comparison purposes I used
the Fairchild data sheets since I find them to usually be the cheapest
and easy to get. Also, if you do a google search for these, the
Fairchild data sheets will be one of the first to pop up.
I first compared the BC547 and BC237, and they're quite similar. The
graph pages look identical. I made the mistake of printing double
sided, so I can't hold them up to the light and see if they're
identical, but they certainly look to be. The specs are very similar,
just minor diffs.
I compared the 2N3904 and BC547 and I found that the values might have
differences that are more influenced by the test, like current and
voltage for the Ft. In the case of the 2N3904, Tr, Tf, etc., are
given but the BC547 had no specs at all for those. And that is
despite the heading for the BC547 that says they're for switching
applications.
The cases for all these transistors is the T0-92, which is identical
in size. The 2N3904 has the standard JEDEC pinout of E B C, whereas
the BCs have it reversed, C B E. The BCs have beta ranges so you can
get a BC237A, B, or C. If you want to change the gain range for the
2N3904, sorry, that's all you get, other than going to the lower gain
2N3903.
I was looking at the EPE mag of a month or two ago (Barnes and Noble
has 'em, but they're always a month or two late). I found that some
projects used the BCs in one place and the 2Ns in another. Why, I
haven't a clue. I would just forget the 2Ns and go with the BC327 and
BC337 for higher current. Here, the Fairchild 2N3904 is 9 cents each,
and the Gen Semi BC547 is 8 cents each. For some odd reason,
Fairchild's BC547 is a much higher 21 cents. But there seems to be no
significant advantage of one over the other.
Maybe if I get some time, I'll make a table with columns for the
different BJTs and rows for the specifications, so they will be side-
by-side for easy comparison. But one data sheet may use Vbr(cbo) and
another may use BV(cbo). Obviously the same, but I can't remember
which is the standard.
Anyway, it's been interesting and enlightening..
--
@@F@r@o@m@@O@r@a@n@g@e@@C@o@u@n@t@y@,@@C@a@l@,@@w@h@e@r@e@@
###Got a Question about ELECTRONICS? Check HERE First:###
http://users.pandora.be/educypedia/electronics/databank.htm
My email address is whitelisted. *All* email sent to it
goes directly to the trash unless you add NOSPAM in the
Subject: line with other stuff. alondra101 <at> hotmail.com
Don't be ripped off by the big book dealers. Go to the URL
that will give you a choice and save you money(up to half).
http://www.everybookstore.com You'll be glad you did!
Just when you thought you had all this figured out, the gov't
changed it: http://physics.nist.gov/cuu/Units/binary.html
@@t@h@e@@a@f@f@l@u@e@n@t@@m@e@e@t@@t@h@e@@E@f@f@l@u@e@n@t@@