Eeyore wrote:
>
> Tim Wescott wrote:
>
>> mrdarrett@[EMAIL PROTECTED]
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
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
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"Applied Control Theory for Embedded Systems" gives you just what it says.
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