The Diode

The main characteristic of a diode is that it conducts electricity in one direction
only. Historically, the first vacuum tube was a diode; it was also known
as a rectifier. The modern diode is a semiconductor device. It is used in all
applications where the older vacuum tube diode was used, but it has the
advantages of being much smaller, easier to use, and less expensive.
A semiconductor is a crystalline material that, depending on the conditions,
can act as a conductor (allowing the flow of electric current) or an insulator
(preventing the flow of electric current). Techniques have been developed to
customize the electrical properties of adjacent regions of semiconductor crystals,
which allow the manufacture of very small diodes, as well as transistors
and integrated circuits.
When you complete this chapter you will be able to do the following:
Specify the uses of diodes in DC circuits
Determine from a circuit diagram whether a diode is forward or reverse
biased
Recognize the characteristic V-I curve for a diode
Specify the knee voltage for a silicon or a germanium diode
Calculate current and power dissipation in a diode
Define diode breakdown
Differentiate between zeners and other diodes
Determine when a diode can be considered ‘‘perfect’’