It was then that later inventors such as Braun, Marconi, Fleming,
and De Forest developed upon the fundamentals established by
the earlier generation of inventors to more practical and useful appliances such as the
radio. This laid the foundation for groups of scientists working at Bell
Laboratories, such as William Shockley, Walter Brattain, John Bardeen, and
numerous others. This led to the advent of the Information Age...
It was the Italian electrical
engineer, Guglielmo Marconi, one of the early pioneers and
inventors of the radio who, using a new technology invented by Nikola
Tesla, sent a radio signal one mile fore the first time. This achievement heralded
the birth of wireless communication. In spite of this, there were still countless
technological barriers to overcome in the quest to perfect wireless communication and make
the technology practical.
In 1874, Ferdinand Braun made an
important discovery to overcome one of the greatest problems in wireless communication.
This was that though a wireless signal could be trans-
mitted over great distances, the receivers at that time were unable to detect these
wireless signals. Braun’s discovery showed that crystals could conduct current in one
direction under specific conditions. This phenomenon was known as rectification.
Amplification
One of the greatest obstacles standing in the path of
wireless communication was the fact that physical barriers and long distances weakened the
radio signal as it travelled through the air. What the crystal sets needed was a radio
signal strong enough to be detected. Yet, on the rare occasion that a signal was detected,
it was so weak, the operators could hardly hear it.
English physicist, John Fleming,
was instrumental in solving this problem. He fitted two electrodes
to a lightbulb and attached it to a radio receiving system, so building his vacuum tube. In this device, electrons flowed from the negatively
charged cathode to the positively charged anode. The current flowing from negative to positive changes the
oscillations of the incoming signal into detectable direct current.
Fleming's vacuum tube was later to be improved by Lee de Forest, an American who modified his tube, and invented the amplifying vacuum tube. He added a third electrode, or grid, a network of small wires around the cathode. Its purpose was to control the flow of electrons from the cathode to the anode. The lower the negative potential of the grid, the more electrons it allowed to flow through the tube, so producing an amplified current.
The vacuum tube was also
instrumental in the development of many other modern devices, including the television,
computers and early telephones. Unfortunately, as these devices were improved, they began
to require something far more compact and reliable than the vacuum tube which was no
longer practical. The ENIAC computer, built at the University
of Pennsylvania is a perfect illustration of this. Because it used so many vacuum tubes
(about 18000), it filled several rooms, and consumed enough power to keep ten homes going.
The vacuum tubes also had other practical problems. It was fragile and bulky, required a
lot of heat to burn out electrons and often burnt out.
The man who actually coined the term 'transistor' was J.R. Pierce, a Bell Labs engineer.
Bell Laboratories and the Transistor
Bell Laboratories
was founded in 1925, bringing together worldclass scientists researching electronics,
chemistry, physics, communications technology and various other disciplines. They
continued where Braun and others had left off, researching the unusual properties of
crystals. Because of the fact that these materials had properties somewhere between those
of conductors and insulators,
they became known as semiconductors.
During the 1930's Bell Labs scientists were working on using ultra-high frequency waves for telephone communication when the problem of detecting these signals arose, as the conventional electron tube detectors were incapable of detecting these waves. The solution to this problem was to be found in an unlikely source, using the redundant "cat's whiskers" detector which was based on a crystal. This discovery led them to looking more closely at silicon, the most reliable semiconductor type.
They found that silicon consisted of two regions, a part that favoured positive current flow, called p, and a part that favoured negative current flow, called n. They further discovered the impurities that caused these tendencies and were able to reproduce them. This discovery of the P-N junction, laid the foundation for the development of not only the transistor, but all semiconductor devices of the future.
In 1945, Bell Labs intensified its semiconductor research when executive director, Mervin Kelly assembled a team of highly skilled solid state physicists. Realising that the vacuum tube had surpassed its potential as an amplification device, they began working on a replacement. Just as De Forest had developed Fleming's vacuum tube by adding a third electrode, the Bell Labs scientists decided to see if doing the same to the semiconductor detector would enable them to control the amount of current flowing through the silicon. This, they hoped, would provide a device that amplified just as the vacuum tube did, but without the massive amount of power and space needed by the vacuum tube.
Three of the physicists working on the project were John Bardeen and Walter Brattain, who
were working on the properties of semiconductors and William
Shockley, who was working on solid state physics. Together they began working with
another type of semiconductor: germanium. Finally, during one
experiment, Brattain noticed that a germanium crystal set in
contact with two wires two-thousandths of an inch apart was amplifying. The many years of
research had finally paid off. They had invented the first semiconductor device that could
do the work of a vacuum tube: the transistor.
One of the first commercial applications of the transistor was a more efficient telephone exchange, early in the 1950's. Other early applications included rural telephone carrier amplifiers and headset amplifiers, as well as the transistorised hearing aid. In 1954, IBM made the first computer devoid of vacuum tubes. It contained 2000 transistors.
The transistor radio came out in 1954, and was an instant hit, so much so, that it became the fastest selling retail object of all time. The term 'transistorized' actually became a selling point. By the late 1950's the transistor was vital in electronic telephone switching systems, but also a key component of other important products and services, such as portable radios, computers, and radar. In the early 1950's, a few years after the transistor was invented, it captured the world's imagination. Here was an amazing new invention that affected the lives of ordinary people.
Over the years, as semiconductor technology improved, the transistor steadily became
faster, cheaper and more reliable. The invention of the integrated circuit in 1959 was a
giant leap forward for the transistor. It allowed a large numbers of transistors and other
electronic components as well as the wiring to be compacted together on a silicon wafer. Where as early transistors had cost between $5 and
$45 to make the millions of transistors compacted onto today's microchips are for all
intents and purposes free. This massive innovation spurred the evolution of the
Information Age. Today's modern microprocessors consist of
millions of transistors, with popular PC chips having as many as 3.5 million transistors.