Learning objectives are stated at the beginning of each chapter. These learning objectives serve as a
preview of the information you are expected to learn in the chapter. The comprehensive check questions
are based on the objectives. By successfully completing the NRTC, you indicate that you have met the
objectives and have learned the information. The learning objective are listed below.
Upon completion of this chapter, you should be able to do the following:
1. State, in terms of energy bands, the differences between a conductor, an insulator, and a
2. Explain the electron and the hole flow theory in semiconductors and how the semiconductor is
affected by doping.
3. Define the term "diode" and give a brief description of its construction and operation.
4. Explain how the diode can be used as a half-wave rectifier and as a switch.
5. Identify the diode by its symbology, alphanumerical designation, and color code.
6. List the precautions that must be taken when working with diodes and describe the different ways
to test them.
INTRODUCTION TO SOLID-STATE DEVICES
As you recall from previous studies in this series, semiconductors have electrical properties
somewhere between those of insulators and conductors. The use of semiconductor materials in electronic
components is not new; some devices are as old as the electron tube. Two of the most widely known
semiconductors in use today are the JUNCTION DIODE and TRANSISTOR. These semiconductors fall
under a more general heading called solid-state devices. A SOLID-STATE DEVICE is nothing more than
an electronic device, which operates by virtue of the movement of electrons within a solid piece of
Since the invention of the transistor, solid-state devices have been developed and improved at an
unbelievable rate. Great strides have been made in the manufacturing techniques, and there is no
foreseeable limit to the future of these devices. Solid-state devices made from semiconductor materials
offer compactness, efficiency, ruggedness, and versatility. Consequently, these devices have invaded
virtually every field of science and industry. In addition to the junction diode and transistor, a whole new
family of related devices has been developed: the ZENER DIODE, LIGHT-EMITTING DIODE, FIELD
EFFECT TRANSISTOR, etc. One development that has dominated solid-state technology, and probably
has had a greater impact on the electronics industry than either the electron tube or transistor, is the
INTEGRATED CIRCUIT. The integrated circuit is a minute piece of semiconductor material that can
produce complete electronic circuit functions.