_________________________________________________________________ Semiconductor Diodes
As radar took on greater importance and C-E equipment became more
sophisticated, the demands for better solid state devices mounted. The limitations of the
electron tube made it necessary to search for something new and different. An amplifying
device was needed that was smaller, lighter, more efficient, and capable of handling
extremely high frequencies. If progress was to be made, these requirements had to be met.
A serious study of semiconductor materials began in the early 1940's and has continued to
1-10. The discovery of the POINT-CONTACT TRANSISTOR in June 1948 was a
significant breakthrough in semiconductor development. Here was a semiconductor that
could amplify. This discovery brought the semiconductor back into competition with the
electron tube. A year later, JUNCTION DIODES and TRANSISTORS were developed.
The junction transistor was found superior to the point-contact type in many respects. By
comparison, the junction transistor was more reliable, generated less noise, and had higher
power-handling ability than the point-contact type. The junction transistor became a rival
of the electron tube in many uses previously uncontested.
1-11. Semiconductor diodes were not to be slighted. The initial work of Dr. Carl Zener
led to the development of the ZENER DIODE, which is often used today to regulate power
supply voltages at precise levels. More interest in the solid state diode was generated when
Dr. Leo Esaki, a Japanese scientist, fabricated a diode that could amplify. This device,
named the TUNNEL DIODE, has amazing gain and fast switching capabilities. Although it
is used in the conventional amplifying and oscillating circuits, its primary use is in
computer logic circuits.
1-12. Another discovery in the late 1950's was that semiconductor materials could be
combined and treated so that they functioned as an entire circuit or subassembly rather than
as a circuit component. Many names have been given to this solid-circuit concept, such as
1-13. The use of semiconductor devices has become so widespread that it would be
impossible to list all their different applications. Instead, a broad coverage of their specific
application is presented.
1-14. Semiconductor devices can be found in just about every commercial product we
use (from the family car to the pocket calculator). Semiconductor devices have even found
their way into television sets, portable radios, and stereo equipment.
1-15. Science and industry also rely heavily on semiconductor devices. Research
laboratories use these devices in all sorts of electronic instruments to perform tests,
measurements, and many other experimental tasks. Industrial control systems (such as
those used to manufacture automobiles) and automatic telephone exchanges also use
semiconductors. Even heavy-duty versions of the solid state rectifier diode are being used
today to convert large amounts of power for electric railroads. Of the many different
applications for solid state devices; space systems, computers, and data processing
equipment are some of the largest consumers.
1-16. Many types of modern military equipment are literally loaded with semiconductor
devices. Many radar, communication, and airborne equipment are transistorized. Data
display systems, data processing units, computers, and aircraft guidance-control assemblies
are also good examples of electronic equipment that use semiconductor devices. All of the
specific applications of semiconductor devices would make a long impressive list.
23 June 2005