TO-220 pinout standard?

Guest
Is it standard that a TO-220 transistor package is, with the tab up,
with the markings facing you, Base, Collector, Emitter? (for example,
on the TIP31A)

I noticed the TO-92 2N3904 I have is (with the markings facing me) E B
C, and a TO-92 2N2222 data sheet even shows C B E !!!

Michael
 
On Jul 2, 10:32 am, "Tom Biasi" <tombiasi...@optonline.net> wrote:
mrdarr...@gmail.com> wrote in message

news:fd4d48c0-8c69-4c14-b6c9-f090c696beaf@i18g2000prn.googlegroups.com...

Is it standard that a TO-220 transistor package is, with the tab up,
with the markings facing you, Base, Collector, Emitter? (for example,
on the TIP31A)

I noticed the TO-92 2N3904 I have is (with the markings facing me) E B
C, and a TO-92 2N2222 data sheet even shows C B E !!!

Michael

The TO-220 package is used for many devices not just transistors.
The pinout is what the data sheet says it is.
Always consult the data sheet if the leads are not marked.

Tom
Click to expand...


So does this mean it is NOT standard that a TO-220 *transistor*
package is BCE? (with the markings facing you)

Michael
 
On Jul 2, 11:02 am, "Tom Biasi" <tombiasi...@optonline.net> wrote:
mrdarr...@gmail.com> wrote in message

news:1308fc94-659e-4818-898d-bd2830be9198@u12g2000prd.googlegroups.com...



On Jul 2, 10:32 am, "Tom Biasi" <tombiasi...@optonline.net> wrote:
mrdarr...@gmail.com> wrote in message

news:fd4d48c0-8c69-4c14-b6c9-f090c696beaf@i18g2000prn.googlegroups.com...

Is it standard that a TO-220 transistor package is, with the tab up,
with the markings facing you, Base, Collector, Emitter? (for example,
on the TIP31A)

I noticed the TO-92 2N3904 I have is (with the markings facing me) E B
C, and a TO-92 2N2222 data sheet even shows C B E !!!

Michael

The TO-220 package is used for many devices not just transistors.
The pinout is what the data sheet says it is.
Always consult the data sheet if the leads are not marked.

Tom

So does this mean it is NOT standard that a TO-220 *transistor*
package is BCE? (with the markings facing you)

Michael

You will find some that are not that way.

Tom
Click to expand...

Thanks.

Michael
 
mrdarrett@gmail.com wrote:

Is it standard that a TO-220 transistor package is, with the tab up,
with the markings facing you, Base, Collector, Emitter? (for example,
on the TIP31A)
Click to expand...
For pcb layout ? I like to make the central pin 0.1" ? Forward of the
other two. When unheatsunk it also gives greater mechanical stability.

It gives greater pad clearance too.

Graham
 
mrdarrett@gmail.com wrote:

So does this mean it is NOT standard that a TO-220 *transistor*
package is BCE? (with the markings facing you)
Click to expand...
BCE to me, then which way are you looking at it ? READ THE DATASHEET.

Grahan
 
mrdarrett@gmail.com wrote:
Is it standard that a TO-220 transistor package is, with the tab up,
with the markings facing you, Base, Collector, Emitter? (for example,
on the TIP31A)

I noticed the TO-92 2N3904 I have is (with the markings facing me) E B
C, and a TO-92 2N2222 data sheet even shows C B E !!!

Michael
Click to expand...
It is _common_ for a TO-220 transistor to be wired that way, but not
universal.

The manufacturer will pin out the transistor in the way they think is
best; usually this means connecting the collector to the tab for good
heat dissipation, and to the center pin because that's what wants to
connect to the tab (I don't know why center pin = tab; I assume it's for
some sound mechanical reason).

For a while (and perhaps still) there were budget TO-220 RF transistors
that put the emitter on the tab, to reduce the capacitance to ground
from the collector.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" gives you just what it says.
See details at http://www.wescottdesign.com/actfes/actfes.html
 
Tim Wescott wrote:

mrdarrett@gmail.com wrote:
Is it standard that a TO-220 transistor package is, with the tab up,
with the markings facing you, Base, Collector, Emitter? (for example,
on the TIP31A)

I noticed the TO-92 2N3904 I have is (with the markings facing me) E B
C, and a TO-92 2N2222 data sheet even shows C B E !!!


It is _common_ for a TO-220 transistor to be wired that way, but not
universal.

The manufacturer will pin out the transistor in the way they think is
best; usually this means connecting the collector to the tab for good
heat dissipation, and to the center pin because that's what wants to
connect to the tab (I don't know why center pin = tab; I assume it's for
some sound mechanical reason).
Click to expand...
It's the bulk of the die substrate.

Graham
 
Eeyore wrote:
Tim Wescott wrote:

mrdarrett@gmail.com wrote:
Is it standard that a TO-220 transistor package is, with the tab up,
with the markings facing you, Base, Collector, Emitter? (for example,
on the TIP31A)

I noticed the TO-92 2N3904 I have is (with the markings facing me) E B
C, and a TO-92 2N2222 data sheet even shows C B E !!!

It is _common_ for a TO-220 transistor to be wired that way, but not
universal.

The manufacturer will pin out the transistor in the way they think is
best; usually this means connecting the collector to the tab for good
heat dissipation, and to the center pin because that's what wants to
connect to the tab (I don't know why center pin = tab; I assume it's for
some sound mechanical reason).

It's the bulk of the die substrate.

Graham

OK, but why does the mounting tab have to go to the center pin? If it's
Click to expand...
all being stamped out of sheet anyway, why not have the mounting tab
connected to the right pin, or the left?

I assume there's a good reason, because AFAIK the center pin = tab is
just about universal.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" gives you just what it says.
See details at http://www.wescottdesign.com/actfes/actfes.html
 
Tim Wescott wrote:

OK, but why does the mounting tab have to go to the center pin? If it's
all being stamped out of sheet anyway, why not have the mounting tab
connected to the right pin, or the left?

I assume there's a good reason, because AFAIK the center pin = tab is
just about universal.
I think it is all about physical stability of the base and
Click to expand...
emitter lead frames. If they are tucked into a notched
corner of the collector frame, they are stronger than if
they are just hung off the side of the collector frame, as
the far corner lead would be with the base and emitter in
the center and corner positions. Since they are held in
place only with the epoxy cast, having metal around two
sides of the end of the base and emitter lead gives added
rigidity and strength. At least, after blowing a few up and
seeing how they are made, this has been my assumption.

Perhaps Phil or someone who does investigation of explosive
failure has some good photos of the exploded construction.
A dental X-ray or two would be neat to see, also. I know
that a common failure mode I have seen with the TO-126
(smaller than the TO-220 power tab, with the hole through
the epoxy and no exposed metal tab) is the base or emitter
lead frame breaking lose from the epoxy so the bond between
the lead frame and the die breaks.
http://www.fairchildsemi.com/products/discrete/pdf/to126.pdf
The epoxy is just too thin and narrow to have enough
physical strength to handle thermal stresses between board,
transistor and heat sink. For this reason, I have given up
on that package in new designs.

The TO-202, however seems to be fine.
http://www.national.com/ms/TR/TRANSISTOR_OUTLINE__TO-202_.pdf
And some of those do have the collector on the end. So maybe
my hypothesis is all wet. I.e. D40 and D41 series GE
transistors and darlingtons.

But they do put the beveled (weaker) end of the epoxy over
the collector pin, and have the full epoxy thickness over
the emitter on the far corner. Still more rugged than the
TO-126.

--
Regards,

John Popelish
 
You must log in or register to reply here.

Welcome to EDABoard.com

Sponsor

Back
Top