(Not So) Bizarre Transistor Behavior (Yet) Again

[Fred E. Davis]

Last year, I was looking for the Bob Pease articles from Electronic
Design with the reverse-biased transistor puzzle. (I was one of an
unknown number who solved the puzzle.) I had recalled it being an
April Fool's issue, which is one of the red herring's that prevented
my finding the article (it was in the *March* issue). The other
herring was the title "What's All This R-C Filter Stuff, Anyhow?"
which doesn't hint at the puzzler.

In the midst of cleaning up, I found the articles (the puzzle plus the
follow-up answer the next month), scanned them, and posted them on
alt.binaries.images.vintage-engineering, subject header: "Bob Pease
articles, x of 4 pages". In order to keep the file size down, I gave
up gray scale, and poor Mr. Pease's visage is a bit high-contrast.

One of the mysteries that was never resolved in my correspondence with
Mr. Pease concerned the color of the emitted light. He suggested in
the April article that the light was red. However, the tranistor I
observed (by cutting the top off the TO-5 can of a 2N1613) emitted a
greenish-yellow light.

 

[Henry]

Emitted light wave-length is commonly controlled by the band-gap voltage. It
depends on the semi material and dotation.
I think this is also true in your case.
(Does the transistor knows he is one - NO!)
Regards -
Henry


Fred E. Davis schrieb in Nachricht ...

 

[Gerhard]

Last year, I was looking for the Bob Pease articles from Electronic
Design with the reverse-biased transistor puzzle. (I was one of an
unknown number who solved the puzzle.) I had recalled it being an
April Fool's issue, which is one of the red herring's that prevented
my finding the article (it was in the *March* issue). The other
herring was the title "What's All This R-C Filter Stuff, Anyhow?"
which doesn't hint at the puzzler.

Which "March" issue please ?

gvdb

 

[Ian Stirling]

Emitted light wave-length is commonly controlled by the band-gap voltage. It
depends on the semi material and dotation.
I think this is also true in your case.
(Does the transistor knows he is one - NO!)

<snip quoted message incorrectly placed at bottom>

The silicon bandgap voltage inherently creates photons in the deep IR.
You can't see them.
If the other poster was seeing yellow, then that's not it.

 

[Fred E. Davis]

Which "March" issue please ?

gvdb

18 March '96, and 1 April '96. Please see my previous message for the
location where I have posted scanned copies of the articles
(alt.binaries.images.vintage-engineering, subject header: "Bob Pease
articles, x of 4 pages"). They are *not* available on ED's website.

 

[Fred E. Davis]

<snip quoted message incorrectly placed at bottom>

The silicon bandgap voltage inherently creates photons in the deep IR.
You can't see them.
If the other poster was seeing yellow, then that's not it.

Fascinating; I wasn't seeing what I was seeing. It is most definitely
visible light. It may have been a harmonic, but it was certainly
visible as a greenish-yellow. It's intensity varies proportional to
the current.

 

[Fred E. Davis]

<snip quoted message incorrectly placed at bottom>

The silicon bandgap voltage inherently creates photons in the deep IR.
You can't see them.
If the other poster was seeing yellow, then that's not it.

Yes, IR certainly seems feasible for silicon (and the 2N1613 I used is
most definitely silicon). However, I'm willing to look beyond the
visible, so I pulled out an IR-sensitive video camera. Observing the
transistor under 12x magnification, the visible light was clearly
seen. I swung the microscope out of the way and replaced it with the
video camera; the dot of light was still there. I then inserted an IR
pass filter (that strongly attenuates visible light) in the path, and
while the dot of light was still visible, it was attenuated by the IR
pass filter. From this I concluded that yes, there was IR light
present, but that it was not the *only* wavelength present.