By Jonathan Fildes

Science and technology reporter, BBC News



John Bardeen (left), William Shockley (seated) and Walter Brattain (right)

The period of work by John Bardeen and Walter Brattain, working under William Shockley, would become known as the "miracle month" and resulted in the world's first working transistor.

"They demonstrated something that became the basic mechanism for our entire electronic industry," said Dr Art Ramirez of Bell Labs, the location of the 1947 invention.

"They're in aircraft, automobiles, digital cameras and microwave ovens," said Jeff Katz, a guide at the Computer History Museum in Silicon Valley.

"In every house there is somewhere in the region of 50 to 100 million transistors, and that's probably a conservative estimate," he said. "If you start including computers and digital cameras you are probably approaching one trillion."

Computing age

Transistors are used to control the flow of electricity in a circuit.

The flow between two terminals - the source and the drain - is controlled by applying a current or voltage to the third terminal - the gate.

The first transistor consisted of plastic wrapped in gold foil

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"It's very much like a water faucet. The gate is the handle and the faucet controls the flow of electrons between the source and the drain," said Dr Ramirez.

The tiny devices have two key properties which make them attractive to electronics engineers: they can amplify a signal and they can act like a switch.

This ability to boost a signal makes them attractive to the communications and broadcast industry whilst their capability to turn on and off quickly has made them the component of choice for computation.

Their development came from a world recovering from the Second World War.

"During the war there was a lot of electronics work going on for communications and computation mainly for military purposes," said Mr Katz.

For example, in December 1943, the British built Colossus - the first electronic computer - to break messages passed by the German high command.

"This culminated in the invention of the ENIAC computer," said Mr Katz.

TRANSISTOR HIGHLIGHTS 1947: Transistor invented 1952: First - commercial application - hearing aid 1954: First mass-market device - transistor radio 1956: First transistor computer

The ENIAC was installed at the University of Pennsylvania in 1946 and was the first large-scale programmable digital computer.

Like Colossus, instead of transistors it used vacuum tubes, also known as thermionic valves, which were delicate structures that looked similar to light bulbs.

"It filled a room, the power consumption was huge, it had nearly 18,000 tubes but it had very, very limited functionality," said George Scalise president of the Semiconductor Industry Association (SIA).

"There was no way of scaling up the computer without finding some way to make the devices that allowed it to function lower cost, lower power, smaller and more reliable."

Crude device

As a result scientists across the world began to look for an alternative.

One of the leading groups was based at the Bell Telephone Laboratories in New Jersey.

The Sonotone 1010 was the first transistorised product

There, a theoretician known as William Shockley led the solid state physics group, which included other scientists such as John Bardeen and Walter Brattain.

After hiring Bardeen, Shockley set him off on a project to understand the interaction of electrons on the surfaces of semiconductors, but personal differences meant the new recruit soon went his own way.

"Bardeen really didn't get along with Shockley so he started working with Brattain who was an experimentalist," said Dr Ramirez.

Over 18 months the pair went about investigating these "surface states" using various experimental set-ups.

"It was a series of experiments that led to a deeper understanding of how to build a device that actually switched," he said.

The work led to their miracle month and culminated with them showing off the first working transistor two days before Christmas in 1947.

The half-inch (1.25cm) device, made from germanium with two gold contacts held in place by a plastic wedge, bore little resemblance to the tiny precise switches produced today.

"I have seen a replica been made of the first transistor in the same way as it was made and it's remarkably crude," said Mr Katz.

However, it was enough to convince the hierarchy of Bell Labs and after filing patents it was announced to the public on 1 July 1948

"This was announced to fantastic fanfare," said Dr Ramirez. "Reading about it reminds me of the way that Steve Jobs rolls out the iPod."

Silicon block

Over the next few years, Shockley modified the design of the transistor into a device closer to the design used today.

"He made such a key contribution that he was a co-recipient of the Nobel Prize [for Physics] in 1956," said Dr Ramirez.

With the invention of the transistor many new applications become possible, including the first transistor-based hearing aid, made by Sonotone This was followed by the first mass market device - the transistor radio.

"They were about the size of a paperback book today but the replaced something that was about the size of a bread toaster," said Mr Katz.

They were also used for military equipment, televisions and in communications networks.

Initially, transistors were built separately and then wired together to make circuits.

But in 1958, Jack Kilby, a scientist at Texas Instruments, invented the integrated circuit, a circuit where all of the components were built onto a single block of material, commonly silicon.

The transistor had found its natural home and its development has continued ever since.

Elements that used to be measured in millimetres and even centimetres in the first device are now measured in nanometres (billionths of a metre).

Intel's next generation of chip, for example will pack more than four hundred million transistors into an area the size of a postage stamp.

The silicon industry is now worth almost $300bn a year and plays a key role in almost every area of life from computing and health care to entertainment and global communications.

"Nothing else could have transformed the world to the extent that this has," said Mr Scalise.