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The transistor is a Solid State Semiconductor Device that can be used for Amplification , Switch ing, voltage stabilization, signal modulation and many other functions. It allows a variable current, from an external source, to flow between two of its terminals depending on the voltage or current applied to a third terminal. Transistors are made either as separate components or as part of an Integrated Circuit .


INTRODUCTION


Transistors are divided into two main categories: ''bipolar junction transistors'' ( BJT s) and ''field effect transistors'' ( FET s). Transistors have three terminals where, in simplified terms, the application of current (BJT) or voltage (FET) to the input terminal increases the Conductivity between the other two terminals and hence controls current flow through those terminals. The physics of this "transistor action" are quite different for the BJT and FET; see the respective articles for further details.

In Analog Circuit s, transistors are used in Amplifiers , (direct current amplifiers, audio amplifiers, radio frequency amplifiers), and linear Regulated Power Supplies . Transistors are also used in Digital Circuit s where they function as electrical switches. Digital circuits include Logic Gate s, random access memory ( RAM ), and Microprocessors .


HISTORY


The first patents for the transistor principle were registered in Germany in 1928 by Julius Edgar Lilienfeld . In 1934 German physicist Dr. Oskar Heil patented the field-effect transistor. It is not clear whether either design was ever built, and this is generally considered unlikely.

On 22 December 1947 William Shockley , John Bardeen and Walter Brattain succeeded in building the first practical Point-contact Transistor at Bell Labs . This work followed from their war-time efforts to produce extremely pure Germanium "crystal" mixer diodes, used in Radar units as a Frequency Mixer element in Microwave radar receivers. Early tube-based technology did not switch fast enough for this role, leading the Bell team to use solid state Diode s instead. With this knowledge in hand they turned to the design of a Triode , but found this was not at all easy. Bardeen eventually developed a new branch of Surface Physics to account for the "odd" behaviour they saw, and Bardeen and Brattain eventually succeeded in building a working device.

, won an internal ballot. The rationale for the name is described in the following extract from the company's Technical Memoranda calling for votes:

Bell put the transistor into production at Western Electric in Allentown, Pennsylvania . They also licensed it to a number of other electronics companies, including Texas Instruments , who produced a limited run of Transistor Radio s as a sales tool. Another company liked the idea and also decided to take out a license, introducing their own radio under the brand name Sony . Early transistors were "unstable" and only suitable for low-power, low-frequency applications, but as transistor design developed, these problems were slowly overcome. Over the next two decades, transistors gradually replaced the earlier Vacuum Tube s in most applications and later made possible many new devices such as Integrated Circuit s and Personal Computer s.

Shockley, Bardeen and Brattain were honored with the Nobel Prize In Physics "for their researches on semiconductors and their discovery of the transistor effect". Bardeen would go on to win a second Nobel in physics, one of only two people to receive more than one in the same discipline, for his work on the exploration of Superconductivity .

In August 1948 German physicists Herbert F. Mataré (1912– ) and Heinrich Walker (ca. 1912–1981), working at Compagnie Des Freins Et Signaux Westinghouse in Paris , France applied for a patent on an amplifier based on the minority carrier injection process which they called the "transistron." Since Bell Labs did not make a public announcement of the transistor until June 1948, the transistron was considered to be independently developed. Mataré had first observed transconductance effects during the manufacture of germanium duodiodes for German radar equipment during WWII . Transistrons were commercially manufactured for the French telephone company and military, and in 1953 a solid-state radio receiver with four transistrons was demonstrated at the Düsseldorf Radio Fair.


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