Index Home About Blog
From: (Dave Platt)
Newsgroups: sci.electronics.components
Subject: Re: Reverse biasing the base emitter junction
Date: Wed, 08 Nov 2000 03:36:45 -0000

In article <>,
Boris Mohar  <> wrote:
>>I was so excited after I read Bob Pease's article, I went to my lab and
>cut off the top of a
>>plain ol' 2n2222.  Biased it up (sorry- don't remember exactly now, but
>I saved the article), and the junction was
>>glowing.  And sure enough, a DVM indicated a negative voltage across one of the
>>terminals with respect to the bias power supply's common and + leads.
> There are certain eproms that light up when put in backwards I was
>told.  They also stop being eproms.  That one I did not try.

It gets even better than that.

I was told a story by a guy (Hi, Greg!) who used to work for a company
which was developing a high-performance CPU compatible with the Sun
SPARC architecture.  They'd spent the best part of a year designing
the CPU, working the bugs out of its architecture via simulation, and
actually laying out the chip.

Finally, they got the first sample back from the fab.  Nice big
ceramic case, with a clear quartz inspection lid over the top so they
could use a microscipe to perform visual checks for defects, etc.

They put it in the test motherboard, and very carefully powered it up.
Lo and behold, after a bit of fiddling around they got it to wake up
and start running test diagnostics.

One of the engineers thought "Hey, we need a record of this - first
code running!"  He pulled out his 35mm camera, and took a photo of the
board and CPU.

His big mistake - he turned on the camera's flash attachment.

The resulting short, bright flash of light went right through the
quartz lid of the CPU package.  It had enough bright, short-wavelength
(violet and near-UV) content to trigger photoconduction in the surface
layers of the CPU chip.

A good percentage of the gates in the chip immediately, and
enthusiastically went into SCR breakdown, and shorted +5 to ground.


There was a bright flash of light across the whole surface of the
chip, as it completely fried itself.  It never worked again.

That was one _expensive_ photograph!

Dave Platt                                 
Visit the Jade Warrior home page:
  I do _not_ wish to receive unsolicited commercial email, and I will
     boycott any company which has the gall to send me such ads!

Index Home About Blog