Transistor Amplifiers
Magno Urbano · 2019
This chapter examines the usage of transistors as amplifiers. It shows how transistors are able to "amplify" signals and introduces the reader to how they work. In fact, transistors are like switches that can manipulate and modulate the voltage coming from the power supply to generate a huge copy of the input signal, creating the illusion of amplification. Different transistors offer different values for the current gain, which can vary from 10, 20, and 50 to values like 800. In an amplifier, the output should never exceed the rails or distortion will appear at the output, and damage can happen to the power supply. To work as an amplifier, a transistor must be configured properly to operate within a certain range of parameters. This operating point is called "quiescent operating point" or "Q-point." Transistors can be used to create amplifiers in very different ways, called"classes." Every class is more or less energy efficient than another.