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Postby TGTS0907129» Concept of transistors

Describe the concept of transistors


The properties of semiconductors can be used to construct nonlinear circuit elements which have certain advances over the electron tubes disused in the 1950s, Bardeen, Brattain   and Shockley, at the Bell Telephone Laboratories, did pioneer work in growing crystals of semiconducting materials of extraordinary purity and then modifying them with minute traces of another element to obtain desirable conduction properties.
An example of the semiconductor is germanium has few electrons available for conduction and hence is a poor conductor. When minute traces of an impurity, for example, antimony, which is capable of supplying conduction electrons, are added to the germanium, the conduction is slightly increased. With this type of impurity the negative conduction elements are free to migrate within the crystal, and hence this is called n-type germanium. If instead, a different impurity is added, for example gallium, which is able to harrow electrons from the germanium, gaps, or “holes,” appear in the structure that are electron defleciencies and therefore equivalent to positive charges. The holes may migrate through the crystal and furnish the equivalent of a moving positive charge. This is called p-type germanium. Both types of germanium are used in making transistors. Other semiconductors are also used.

A second kind of transistor is the junction type. It consists of this section, the two end sections of the same type, type, n or p, and the central section of the other, p or n. They would be labeled n-p-n or p-n-p type. For the n-p-n type the emitter and collector voltage are negative and positive, respectively. Junction transistors are more stable as amplifiers than point contact transistors, and give higher power gain and less noise.

Certain advantages of the transistor over an electron tube are quite apparent. The transistor is much smaller than the tube, and thus the circuit can be more compact. No energy is necessary to heat a filament; thus there is a saving in space and weight by elimination of the heater source. The elimination of the filament also tends to increase stability in the circuit and to permit longer life.

By TGTT170912123 on 10/23/2015 12:24:47 AM
TGTS0907129 on 10/22/2015 11:14:37 PM

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