Chapter Overview

An amplifier needs an ac input signal to produce an ac output signal but an oscillator doesn’t. An oscillator is a circuit that creates an ac signal. Oscillators can be designed to produce many kinds of waveforms such as sine, rectangular, triangular, or sawtooth. The range of frequencies that oscillators can generate is from less than 1 Hz to well over 10 gigahertz (10 GHz = 1 X 1010 Hz). Depending on the waveform and frequency requirements, oscillators are designed in different ways. This chapter covers some of the most popular circuits, and it also discusses undesired oscillations.

This chapter will help you to:

1. Identify oscillator circuits.

2. Apply the concepts of gain and feedback to oscillators.

3. Predict the frequency of operation for oscillators.

4. List causes of undesired oscillations.

5. Identify techniques used to prevent undesired oscillation.

6. Troubleshoot oscillators.

7. Explain and troubleshoot direct digital synthesizers.

Study Outline

11-1 Oscillator Characteristics

11-2 RC Circuits

11-3 LC Circuits

11-4 Crystal Circuits

11-5 Relaxation Oscillators

11-6 Undesired Oscillations

11-7 Oscillator Troubleshooting

11-8 Direct Digital Synthesis

11-9 DDS Troubleshooting