Re: TO-220 pinout standard?

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