Transistors, Vacuum Tubes, Filtering and Amplifier

In this PDH or CE course the student will learn about the basics of transistors, vacuum tubes, filtering and amplifiers. The transistor is a three-terminal device primarily used to amplify signals and control current within a circuit. [Figure 10-206] The basic two-junction semiconductor must have one type of region sandwiched between two of the other type. The three regions in a transistor are the collector (C), which is moderately doped, the emitter (E), which is heavily doped and the base (B) significantly less in its doping.

The alternating layers of semiconductor material type provide the common commercial name for each type of transistor. The interface between the layers is called a junction. Selenium and germanium diodes previously discussed are examples of junction diodes. Note that the sandwiched layer or base is significantly thinner than the collector or the emitter. In general, this permits a “punching through” action for the carriers passing between the collector and emitter terminals.

Originally, vacuum tubes were developed for radio work. They are used in radio transmitters as amplifiers for controlling voltage and current, as oscillators for generating audio and radio frequency signals, and as rectifiers for converting alternating current into direct current. While there are many types of vacuum tubes for a variety of applications, the most common types fall into one of the following families:

1. diode
2. triode
3. tetrode
4. pentode

An amplifier is a device that enables an input signal to control an output signal. The output signal will have some or all of the characteristics of the input signal but will generally be a greater magnitude than the input signal in terms of voltage, current, or power. Gain is the basic function of all amplifiers. Because of this gain, we can expect the output signal to be greater than the input signal.

Learning Objective:

The learning objective of this PDH or CE continuing education course is the students to learn about the basics of transistors, vacuum tubes, filtering and amplifiers.

Review the quiz before studying the course.

Course Content

Course Author: Franco F. Davati, P.E.