| Topic: |
Science > Physics |
| User: |
"vikb" |
| Date: |
02 Jul 2007 08:12:00 PM |
| Object: |
thermionic emission /diode |
Hello,
I want to understand conceptually the fundamentals of a diode
operation. Can anyone enlighten?
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| User: "Tom Potter" |
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| Title: Re: thermionic emission /diode |
03 Jul 2007 07:24:23 AM |
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"vikb" <vikmere@gmail.com> wrote in message
news:1183425120.276110.43230@a26g2000pre.googlegroups.com...
Hello,
I want to understand conceptually the fundamentals of a diode
operation. Can anyone enlighten?
The diode,
like audio and picture recording and the electrical power industry
was invented by Thomas Edison.
Edison discovered the "Edison Effect" about 1880 and patented it in
1884.
He discovered the effect while searching for
a way to use his incandescent lamp,
as a monitoring device to indicate variations
in the output of electrical generators,
that were more effective that the flickering of the lamp.
He placed a conductor inside of a lamp,
and observed that a current flowed
from the heated filament in the lamp
to the conductor.
Edison's invention of the "diode"
lead to the discovery of the electron
by J. J. Thomson in 1887,
and to modern electronics.
In 1906, Lee Deforrest added a "control grid"
between the electron emitter "cathode"
and the electron collector "plate".
thus inventing the "triode" which provided
a means for amplifying weak electrical signals.
In 1906 Greenleaf Whittier Pickard patented
a crystal version of Edison's "diode" detector,
called a "cat's whisker". The cat's whisker" diode
didn't amplify, but it was a much more sensitive
"detector" that other detectors.
In 1925 Julius Edgar Lilienfeld patented
a "field effect transistor" which was basically
a solid sate version of the triode,
combined with the "cat's whisker" idea.
In 1945, after WWI, and after Lilienfeld's patents expired,
Bell Labs hacked the point contact, germanium transistor.
which was based on the "cat's whisker" diode,
and the triode, and others followed up
adopting Lilienfeld's field effect approach.
Note that as AT&T was by far the largest electronic based
company, and needed billions of audio amplifiers,
it was in AT&T's best interests to wait for the transistor
patents to expire before "inventing" their own.
AT&T then licensed a number of companies
to use the patent they got on this device.
Texas Instruments, a small, unknown company in Texas,
got a license, and they got the idea to create the
"control grid", not by sticking a "cat whisker" into the crystal,
but by changing the qualities of a surface in the crystal by
"doping" the crystal with impurities. In other words, they
added the "control grid" by doping, rather than by point contact.
Texas Instrument, led by an ENGINEER, rather than a physicist,
managed to create the first silicon, junction transistors.
These had many advantages over the point contact transistors,
and of course Texas Instruments made billions of dollars.
TI, and others, notably Fairchild, got the idea,
that with all this space laying around unused,
why not put more than one transistor on a crystal,
and they did. They also go the idea to "dope" the
crystals to add resistance and capacitance,
and these devices were called "integrated circuits."
Now the race was on to put more and more
devices (Transistors, resistors and capacitors)
on a single crystal, but the problem was not the
idea, it was the technology. There was a certain
probability of a particular component failing, and the more
components you put on a single crystal, the more
likely the device was to fail. So the problem boiled
down to growing more pure crystals, to be able to
precisely put the "doping" where you wanted it, etc.
Slowly, as advances were made in many areas,
it became possible to put more and more
components onto a single crystal.
Note that all of these advances were made by
engineers, production people, clean room people,
people from the printing and optical industries, etc.
No knowledge of quantum mechanics was used in this pursuit.
Just plain hard, slow progress.
At this point, many kinds of "integrated circuits" were
manufactured, audio amplifiers, gates, flip flops, etc.
and a new company was formed to try to make
a complex, programmable kind of integrated circuit
for a communication application.
Whereas the previous devices were logic blocks
that had to be assembled onto
a printed circuit, the Intel device was internally programmable,
so if you wanted to change the logic of a circuit,
you didn't have to make a whole new board, you
could just reprogram the integrated circuit itself.
This device (The Intel 4040) was called a micro-processor.
Although the 4040 was not a commercial success, Intel made a more
powerful chip called the 8080, and after a television service magazine
ran an article on it, folks all over the nation began trying to
use it to make their own personal computers.
Soon a few companies, including Altair, MITS, and Apple
began to make personal computers to sell to the public,
and it wasn't long before Radio Shack, Commodore, TI,
and others got on the bandwagon.
But cut the question posed,
a diode is a device is a one way street
for electricity. There are many ways to make
one way streets for electrons, protons,
charged particles and molecules.
As you are interested in vacuum tube diodes
consisting of a heater, cathode and plate,
I suggest that you do a Google image search on
"thermionic diode".
Pardon my "blustering"
but I just wanted to toss in a little electronic history,
to counter the Urban Legends.
--
Tom Potter
*** Time Magazine Person of the Year 2006 ***
*** May 2007 Anti-Bigot Award ***
http://home.earthlink.net/~tdp
http://tdp1001.googlepages.com/home
http://no-turtles.com
http://www.frappr.com/tompotter
http://photos.yahoo.com/tdp1001
http://spaces.msn.com/tdp1001
http://www.flickr.com/photos/tom-potter
http://tom-potter.blogspot.com
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| User: "Jan Panteltje" |
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| Title: Re: thermionic emission /diode |
03 Jul 2007 05:13:39 AM |
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On a sunny day (Tue, 03 Jul 2007 01:12:00 -0000) it happened vikb
<vikmere@gmail.com> wrote in
<1183425120.276110.43230@a26g2000pre.googlegroups.com>:
Hello,
I want to understand conceptually the fundamentals of a diode
operation. Can anyone enlighten?
Thermionic right?
Scenario:
Vacuum glass tube, no air, 2 pieces of metal in it, one a wire, the other
a metal plate some distance away from the wire.
Action:
The metal wire is heated by a current (like a light bulb), electrons become
wild and are jumping around...:-) Can easily leave the wire, hang around it in a cloud.
Explanation of terms:
This hot metal wire is called the 'cathode'.
The metal plate is called the 'anode'.
More Action:
The metal plate is made negative relative to the wire.
Result:
Electrons, who are negative, do not go to the metal plate, similar charges repel each other.
Final action:
The metal plate is now made positive relative to the cathode, the electrons on the cathode that
where jumping about because of hot feet, now move towards the positive metal plate.
Opposite charges attract.
So electrons can only flow from cathode to anode, ONE WAY.
Note:
If electrons land with enough energy on the anode then the anode will also get hot,
and become a cathode....
So there is a limit to how many electrons per time (= current) can make the trip.
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| User: "" |
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| Title: Re: thermionic emission /diode |
02 Jul 2007 08:55:02 PM |
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vikb <vikmere@gmail.com> wrote:
Hello,
I want to understand conceptually the fundamentals of a diode
operation. Can anyone enlighten?
Perhaps Google with 559,000 hits for diode fundamentals?
--
Jim Pennino
Remove .spam.sux to reply.
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| User: "vikb" |
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| Title: Re: thermionic emission /diode |
02 Jul 2007 11:18:45 PM |
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On Jul 2, 6:55 pm, wrote:
vikb <vikm...@gmail.com> wrote:
Hello,
I want to understand conceptually the fundamentals of a diode
operation. Can anyone enlighten?
Perhaps Google with 559,000 hits for diode fundamentals?
--
Jim Pennino
Remove .spam.sux to reply.
My question is that there are two batteries connected. One that lights
the filament and the other that is connected to the anode. But arent
the two batteries connected to each other and does not that create a
problem?
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| User: "" |
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| Title: Re: thermionic emission /diode |
03 Jul 2007 10:25:03 AM |
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vikb <vikmere@gmail.com> wrote:
On Jul 2, 6:55 pm, wrote:
vikb <vikm...@gmail.com> wrote:
Hello,
I want to understand conceptually the fundamentals of a diode
operation. Can anyone enlighten?
Perhaps Google with 559,000 hits for diode fundamentals?
--
Jim Pennino
Remove .spam.sux to reply.
My question is that there are two batteries connected. One that lights
the filament and the other that is connected to the anode. But arent
the two batteries connected to each other and does not that create a
problem?
Perhaps Google with 3,740 hits for "vacuum tube diode".
--
Jim Pennino
Remove .spam.sux to reply.
.
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| User: "Sam Wormley" |
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| Title: Re: thermionic emission /diode |
02 Jul 2007 09:05:34 PM |
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vikb wrote:
Hello,
I want to understand conceptually the fundamentals of a diode
operation. Can anyone enlighten?
Diode
http://en.wikipedia.org/wiki/Diode
The P-N Junction Diode
http://hyperphysics.phy-astr.gsu.edu/hbase/hframe.html
Forward Biased P-N Junction
http://hyperphysics.phy-astr.gsu.edu/hbase/solids/diod.html
Child-Langmuir Law
http://scienceworld.wolfram.com/physics/Child-LangmuirLaw.html
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