Introduction to the Transistor

The transistor is undoubtedly the most important modern electronic component
because it has enabled great and profound changes in electronics and in
our daily lives since its discovery in 1948.
This chapter introduces the transistor as an electronic component that acts
similarly to a simple mechanical switch, and, in fact, it is actually used as a
switch in many modern electronic devices.Atransistor can be made to conduct
or not conduct an electric current — exactly what a mechanical switch does.
Most transistors used in electronic circuits are bipolar junction transistors
(BJT), commonly referred to as bipolar transistors, junction field effect transistors
(JFET), or metal oxide silicon field effect transistors (MOSFET). This chapter
(along with Chapters 4 and 8) illustrates how BJTs and JFETs function and
how they are used in electronic circuits. Because JFETs and MOSFETs function
in similar fashion, MOSFETs are not covered here.
An experiment in this chapter will help you to build a simple one-transistor
switching circuit. You can easily set up this circuit on a home workbench.
You should take the time to obtain the few components required and actually
perform the experiment of building and operating the circuit.
In Chapter 4, you will continue to study switching designs and the operation
of the transistor as a switch. In Chapter 8, you learn how a transistor can be
made to operate as an amplifier. In this mode, the transistor produces an
output that is a magnified version of an input signal, which is useful because
many electronic signals require amplification. These chapters taken together
present an easy introduction to how transistors function and how they are
used in basic electronic circuits.
71