History of Radio and Electronics

The Audion

It was not until 1911 that the vacuum tube was used as an amplifier. After this discovery people were quick to try to exploit it. De Forest built an amplifier using three Audions and demonstrated it to the telephone company A.T & T. Although the performance was poor they saw its potential and soon started to build repeaters using vacuum tubes which they had improved. Naturally as soon as the tube was used as an amplifier, people were quickly able to use it as an oscillator. Indeed, one of the problems soon encountered was difficulties in preventing oscillations in view of the high values of grid anode capacitance.

Note the brass base and the four pins for connection to the outside world. With the first valves or tubes now available, at least in the laboratory, the way was set to further develop the technology and improve their performance.

Transistor History

- history of the development of the transistor - how it was developed, the main names of Bardeen, Brattain, and Shockley.

The transistor history tells of a development that took many years. It built on many years of theoretical research into semiconductors.

First semiconductor diodes arrived and these were able to deliver improved performance over thermionic predecessors in some areas.

However the transistor history is a testament to the perseverance of the researchers who were finally rewarded with the first semiconductor amplifying device.

Bardeen, Brattain, and Shockley were the names that are remembered within the transistor history, but there were many others along the way, who also contributed to the final invention of the bipolar transistor.

Transistor history foundations

The first foundations in the transistor history were set in place many years before. Even in the nineteenth century it had been observed that a class of materials had some unusual electrical properties. These semiconductors had a negative coefficient of resistivity, they were able to rectify electrical currents and they exhibited a photoelectric effect.

Another early use of semiconductors was for the "cat's whiskers" which were detectors used in radio sets. Although they were cheap, there were notoriously unreliable.

Although there was comparatively little interest in semiconductors at this stage of the transistor history before the Second World War, but some developments did occur. Copper oxide and selenium rectifiers started to be used, particularly in applications like battery chargers. The photoelectric effect was also exploited in photographic exposure meters. However their use was relatively limited.

However some development of semiconductor devices occurred in the 1920s and 1930s, most of the theoretical research into the sub-molecular physics was directed towards thermionic technology. This was because even small advances in this field would produce large rewards and a handsome return on investment.

Diode developments

One of the major motivators in the history of the transistor and the development of semiconductor technology in general was the Second World War. One of the greatest advantages which Britain held over Germany was the use of Radar. Operating on relatively high frequencies the need for high performance high frequency components became even more acute. Semiconductor technology was a major key to performance at the higher frequencies being used.

Experts in all fields associated with the development of semiconductors from the UK and USA were quickly assembled. Work started on producing point contact diodes.

As the work progressed semiconductor diode technology made many strides forwards. Teams on both sides of the conflict made developments which gave devices which a far superior performance to anything that was available before the war.

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