The transistor turns sixty
As described in last month’s Pioneers’ Page, an early method for
amplifying electric signals to produce sound was the carbon microphone. By the
start of the 20th century, thermionic valves (or vacuum tubes) were being used
for amplification in many types of equipment, from telephone systems to radio
Some readers might remember how, in the first half of the last century,
radios containing valves took a while to warm up before sound could be heard.
The glow of these sets may have created a cozy atmosphere, but they were hardly
portable. And vacuum tubes not only gave off heat: they were also bulky and
fragile. It was not until the 1940s that a breakthrough came. It made possible
today’s digital world.
Origin of the name
Bell Telephone Laboratories asked staff to name the new invention, and
accepted the proposal of John R. Pierce. So, the transistor was described as "an
abbreviated combination of the words transconductance (or transfer) and varistor".
Some materials can both conduct electricity and resist its flow. Called
semiconductors, they include the elements germanium and silicon. Under the
influence of electrical fields they can either amplify a signal or close a
circuit. The use of crystals to receive radio waves goes back to the late 19th
century, and research into using such "solid-state" materials was carried out in
the 1920s and 1930s. However, there was incomplete understanding of how these
In 1945, a team of physicists at Bell Telephone Laboratories, in New Jersey,
United States, was asked to investigate the topic. The team was led by William
Shockley, with John Bardeen and Walter Brattain. After two years, Bardeen and
Brattain discovered how to make an amplifying circuit using germanium, which
they showed to Bell executives in December 1947. It later became known as the
transistor — and 2007 sees the 60th birthday of one of the most important pieces
of technology ever invented.
How it worked
The first point-contact transistor comprised two very closely spaced gold
contacts held against a block of germanium, which had a surface layer with an
excess of electrons. When an electric signal arrived through the gold foil, it
injected “holes” into the block. A small change in a current applied to the
metal base below the germanium caused a greater change in the current owing
between the two contacts.
In 1956, Bardeen, Brattain and Shockley shared the Nobel Prize for physics
"for their researches on semiconductors and their discovery of the transistor
effect." It works because pure germanium or silicon are good insulators. But if
contaminated, or "doped", with other substances, they produce either a surplus
of negatively charged electrons, or steal electrons from the semiconductor to
produce "holes" that can carry a positive charge. If you place a negative
electrode against a semiconductor with negative carriers, the current is
blocked. The insulating property can be removed by electrically injecting
positive "holes" that attract the negative carriers.
The world’s first transistor was a "point-contact" type. It was overtaken by
the "junction transistor" invented by Shockley in 1948, which comprised a
"sandwich" of three regions of germanium. This blocked the flow of electricity
both ways until a small current was applied to the middle region to let a much
larger current flow through the whole device. Thus, the transistor could act as
either a switch or an amplifier. The new technology could produce controllable
conductivity — at low cost, little power, small size and good durability.
A mass-market, mobile device
In 1954, the Regency TR-1 transistor radio was
launched as the world’s first mass-produced, mobile communication
Hearing aids were the first application for transistors. Then, in 1953, the
first ever radio using a transistor was demonstrated by the German company
Intermetall at the Düsseldorf Radio Fair. In fact, it used four "transistrons"
developed independently by German physicists Herbert F. Mataré and Heinrich
In the United States the following year, two companies, Texas Instruments and
Industrial Development Engineering Associates, cooperated to make the "Regency
TR-1" that was advertised as "the world’s first pocket radio".
This portability began a revolution. No longer was a radio a piece of
living-room furniture; now, it was a personal accessory. The TR-1 was small but
expensive (USD 49.95, or about USD 400 today), and it was soon overtaken by
transistor radios manufactured in Japan. Nevertheless, with parts that were
specially designed to fit its size, the TR-1 had heralded the development of
miniature electronic components.
Transistor technology had other, far-reaching effects. An expert on the first
transistor radios, Dr Steven Reyer, Professor in the Electrical Engineering and
Computer Science Department at the Milwaukee School of Engineering, United
States, has described the TR-1 as "in some ways, really ushering in the
beginnings of the information age. That is, many of the electronic devices that
we have today are based on the transistor in one form or another — either
individual transistors, as appeared in this radio, or, in the case of personal
computers, many millions of transistors embedded in integrated circuits".
William Shockley (seated), John Bardeen
(centre) and Walter Brattain (right)
Heading for Silicon Valley
Using transistors based on silicon, those integrated circuits (or microchips)
revolutionized the world of computing. They were spearheaded by William
Shockley. After leaving Bell Labs in 1955, he directed a semiconductor research
and manufacturing company at Mountain View, California, United States.
Colleagues went on to form Fairchild Semiconductor Corporation, which developed
some of the first integrated circuits at a location that became part of "Silicon
Shockley later became a professor at nearby Stanford University. A meeting
was held there in 2002 to remember those days. It confirmed (and to answer the
question posed in last month’s Pioneers’ Page) that "Shockley
is the man who brought silicon to Silicon Valley."
Question for next time
|What is the connection between computers and
an automaton called "The Digesting Duck"?