_________________________________________________________________ Semiconductor Diodes
allowable voltage for a transistor is limited to about 200 volts (usually 50 volts or less). A
tube can also handle thousands of watts of power. The maximum power output for
transistors generally ranges from 30 milliwatts to slightly over 100 watts.
1-21. When it comes to ruggedness and life expectancy, the tube is still in competition.
Design and functional requirements usually dictate the choice of devices. However,
semiconductor devices are rugged and long-lived. They can be constructed to withstand
extreme vibration and mechanical shock. They have been known to withstand impacts that
would completely shatter an ordinary electron tube. Although some specially designed
tubes render extensive service, the life expectancy of transistors is better than three to four
times that of ordinary electron tubes. There is no known failure mechanism (such as an
open filament in a tube) to limit the semiconductor's life. However, semiconductor devices
do have some limitations. They are usually affected more by temperature, humidity, and
radiation than are tubes.
MATTER AND ENERGY
1-22. To understand why solid state devices function as they do, we will have to
examine the composition and nature of semiconductors. This entails theory that is
fundamental to the study of solid state devices. Rather than beginning with theory, let us
first become reacquainted with some of the basic information concerning matter and
energy.
ATOMIC STRUCTURE
1-23. The universe, as we know it today, is divided into two parts, matter and energy.
Matter, is anything that occupies space and has weight. Rocks, water, air, automobiles,
clothing, and even our own bodies are good examples of matter. From this, we can
conclude that matter may be found in any one of the following three states:
Solid.
Liquid.
Gaseous.
All matter is composed of either an element or combination of elements. An element is a
substance that cannot be reduced to a simpler form by chemical means. Examples of
elements with which you are in contact with every day are iron, gold, silver, copper, and
oxygen. Presently, matter consists of over 100 known elements.
1-24. As we work our way down the size scale, we come to the atom, the smallest
particle into which an element can be broken down and still retain all its original
properties. However, the atom of one element differs from the atoms of all other elements.
Since there are over 100 known elements, there must be over 100 different atoms, or a
different atom for each element.
1-25. Let us consider more than one element at a time. This brings us to the term,
"compound." A compound is a chemical combination of two or more elements. Water,
table salt, ethyl alcohol, and ammonia are all examples of compounds. The smallest part of
a compound, which has all the characteristics of the compound, is the molecule. Each
molecule contains some of the atoms of each of the elements forming the compound.
1-26. Let us consider sugar. Sugar in general terms is matter, since it occupies space and
has weight. It is also a compound because it consists of two or more elements. Take a lump
of sugar and crush it into small particles; each of the particles still retains its original
23 June 2005
TC 9-62
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