Chapter 9
Oscillators
This chapter introduces you to oscillators. An oscillator is a circuit that produces a continuous output signal. There are many types of oscillator circuits used extensively in electronic devices. Oscillators can produce a variety of different output signals, such as sine waves, square waves, or triangle waves.
When the output signal of an oscillator is a sine wave of constant frequency, the circuit is called a sine wave oscillator. Radio and television signals are sine waves transmitted through the air, and the 120-volts AC from the wall plug is a sine wave, as are many test signals used in electronics.
This chapter introduces three basic sine wave oscillators. They all rely on resonant LC circuits as described in Chapter 7, “Resonant Circuits,” to set the frequency of the sine wave.
When you complete this chapter, you will be able to do the following:
- Recognize the main elements of an oscillator.
- Differentiate between positive and negative feedback.
- Specify the type of feedback that causes a circuit to oscillate.
- Specify at least two methods of obtaining feedback in an oscillator circuit.
- Understand how resonant LC circuits set the frequency of an oscillator.
- Design a simple oscillator circuit.
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