If i still remember correctly, a BJT will work in reverse active mode when
you swap its collector & emitter. In this mode, current that powers your LED
still flow into the emitter and out to the collector, but at a percentage of
the base current which now flows to out to the collector too.

Regards,
Tan Chun Chiek

----- Original Message -----
From: "Matthew Brush" <matthewbrush@YAHOO.CA>
To: <PICLIST@MITVMA.MIT.EDU>
Sent: Sunday, June 06, 2004 3:58 AM
Subject: Re: [EE:] Simple Transistor Question


> The wierdest part is that the 2N2222's I have work in either direction,
that
> is, with that LED circuit I posted.  That only adds to the confusion.  So
I
> guess from now on, I'll just order my transistors from Digikey and go by
the
> datasheet of the specific model.
>
> Is it normal for a transistor to "work" in either direction?  My
assumption
> is that they CAN be reversed (C & E) but are supposed to be used in a
> specific direction.
>
> Thanks for the clarification guys.  Peace
>
> MJ Brush
>
> ----- Original Message -----
> From: "rixy04" <rixy04@VVALLEY.COM>
> To: <PICLIST@MITVMA.MIT.EDU>
> Sent: Saturday, June 05, 2004 3:36 PM
> Subject: Re: [EE:] Simple Transistor Question
>
>
> > You cannot arbitrarily swap pinouts. It will only work in one
> configuration. Just because the Radio Shack packaging says one thing
doesn't
> make it right. Sometimes when the vendor prints the drawing they may look
at
> it from the top or the bottom. It will only work one way.
> >
> > Also be aware that the flat side may or may not be the same on different
> manufacturers package. An example is the BS170 and the BS170P. The lead
> configuration is SGD or DGS.
> >
> > You have the right idea as far as your drawing goes. Look at this page
for
> other suggestions:
> > http://www/pic101.com/interface.htm
> >
> > Rick
> >
> > Matthew Brush wrote:
> >
> > > Hi all,
> > >
> > > Something has been bothering me for a while.  I know there was
recently
> a question posted about transistor pinouts, but I was still left with
mixed
> answers on this.
> > >
> > > I have attached a (crappy) drawing I quickly made in photoshop to go
> with this question.
> > >
> > > The package of 2N2222 transistors I bought from RadioShack has pinouts
> on the back which seem to go against what actually works for me, and is
also
> the opposite of how Eagle Layout wires the transistor (from a
> schematic->make board).  Eagle wires it the way that is in the picture,
> which is also how I've been wiring it all along.
> > >
> > > It seems these transistor will work in either direction, but as I'm
soon
> to be attempting an audio circuit (as opposed to the usual turning on a
> relay or whatever), I want to make sure I have it right.
> > >
> > > Is this circuit in the attached GIF correct, labelled properly and
> whatnot?  I would assume that the collector "collects" electricity and
when
> the base is positive, the emmitter "emits" electricity towards ground.
But
> it seems like I'm getting confused going from the schematic to the actual
> circuit.
> > >
> > > Thanks for any clarification anyone can offer as to why i see these
> standard NPN transistors wired differently (ie backwards) sometimes and
not
> others.
> > >
> > > Peace
> > >
> > > MJ Brush
> > >
> > > --
> >
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