13Semiconductors: And Their Junctions
13.1 Introduction
In this chapter, we will examine semiconductors, diodes, transistors, and other components that changed electronics forever.
13.2 It All Started with a Light Bulb
A light bulb is composed of a filament inside a vacuum glass enclosure. This filament is made of a heat‐resistant material, like tungsten, that can become incandescent for long periods of time without melting.
The incandescence produces light and emits a cloud of electrons around the filament.
Figure 13.1 shows a light bulb with an incandescent filament and a cloud of electrons, represented by orange circles with the minus sign.
Electrons are negative charges. What would happen if a metallic plate was added to the light bulb and charged with a positive charge? Remember that opposite charges attract themselves.
Figure 13.2 shows a light bulb with a metallic plate at the opposite end. The metallic plate is connected to the positive of a couple of batteries in series.
Figure 13.1 A light bulb.
Figure 13.2 A primitive vacuum tube.
As expected, the positive plate will attract the electrons from the filament cloud. The bigger the plate’s ...
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