BOOK_CONTENT
From Electronic Devices and Amplifier Circuits with MATLAB Computing, Second Edition

This chapter begins with an introduction to sinusoidal oscillators. Subsequently, we will discuss the RC phase-shift and LC oscillator families, and we will describe the Armstrong, Hartley, Colpitts, crystal, and the crystal-controlled Pierce oscillators.

10.1 Introduction to Oscillators

An oscillator may be defined as a class of wave generators that produce sinusoidal, square, triangular, and sawtooth waveforms. Non-sinusoidal oscillators are known as relaxation oscillators. In Chapter 5 we introduced the Wien bridge oscillator, and in Chapter 7 the family of multivibrators. In this chapter we will be concerned with oscillators that produce sinusoidal waveforms. An oscillator is essentially an amplifier circuit that provides its own input signal Oscillators are classified in accordance with the waveshapes they produce and the circuitry required to produce the desired oscillations. Henceforth, in this chapter, unless otherwise specified, the term oscillator will mean a sinusoidal oscillator.

10.2 Sinusoidal Oscillators

As the name implies, a sinusoidal oscillator produces a sine-wave output signal An ideal oscillator should produce an output signal with constant amplitude with no variation in frequency. But a practical oscillator cannot meet these criteria, the degree to which the ideal is approached depends on the class of amplifier operation, amplifier characteristics, frequency stability, and amplitude stability. Sinusoidal oscillators generate signals ranging from low audio frequencies to ultrahigh radio and microwave frequencies. Many low-frequency oscillators use resistors and capacitors to form their frequency-determining networks and are referred to as RC oscillators. These are used in the audio-frequency range.

Other types of employ inductors...

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Oscillators
Oscillators are devices that are used to generate repetitive signals. They produce output signals without an input signal. There are two major types of electronic oscillators: harmonic oscillators and relaxation oscillators. Harmonic oscillators produce sine wave outputs. Relaxation oscillators produce non-sine wave outputs such as square wave, rectangular wave, and sawtooth outputs.
Audio Analyzers
Audio analyzers measure the noise and audio spectrum of output from an amplifier or a stereo.
Signal Generators
Signal generators and waveform generators are used to test and align all types of transmitters and receivers, to measure frequency and to generate a signal, waveform or noise source. Signal generators can use AC energy, audio frequency (AF) and radio frequency (RF) to function.
Frequency Synthesizers
Frequency synthesizers are electronic devices that generate frequencies by using a combination of other frequencies.
Unijunction Transistors (UJT)
Unijunction transistors (UJT) are three-terminal devices that exhibit a negative resistance characteristic.

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