ELECTRONIC PRINCIPLES - OD1647 - LESSON 1/TASK 2
because they are small, rugged, require no filament power, and
operate at low voltages with comparatively high efficiency. The
development of a family of transistors has even made possible
the miniaturization of electronic circuits.
Transistors have infiltrated virtually every area of science and
industry, from the family car to satellites. Even the military
depends heavily on transistors. The ever increasing uses of
transistors have created an urgent. need for sound and basic
information regarding their operational.
a. Transistor Fundamentals. The first, solid state device
discussed was the twoelement semiconductor diode. The next
device on our list is even more unique. It not only has one
more element than the diode but it can amplify as well.
Semiconductor devices that have three or more elements are
called TRANSISTORS. The term transistor was derived from the
words TRANSfer and resISTOR. The term was adopted because it
best describes the operation of' the transistorthe transfer of
an input signal current from a lowresistance circuit to a high
resistance circuit. Basically, the transistor is a solidstate
device that amplifies by controlling the flow of current
carriers through its semiconductor materials.
There are many different types of transistors, but their basic
theory of operation is all the same. The theory used to explain
the operation of a transistor is the same as that theory used
earlier with the PNjunction diode, except that two such
junctions are required to form the three elements of a
transistor.
b. Elements of a Transistor. The three elements of the two
junction transistor are:
(1) The EMITTER, which gives off, or "emits," current carriers
(electrons or holes);
(2) The BASE, which controls the flow of current carriers; and
(3) The COLLECTOR, which collects the current carriers.
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