RF Power Amplifier, 2nd Edition

Chapter 12Oscillators

12.1 Introduction

An oscillator is a circuit that produces a periodic output signal without any ac input signal. Sinusoidal-tuned resonant oscillators [1–58] are widely used in instrumentation and test equipment as function generators and local signal oscillators in amplitude modulation (AM), frequency modulation (FM), and wireless receivers and transmitters operated in a wide range of frequencies. In radio systems, sinusoidal oscillators establish the transmitter carrier frequency and drive the mixer stages that convert signals from one frequency to another. oscillators also form an integral part of voltage-controlled oscillators (VCOs) used in communication and digital systems. Power oscillators also find a wide range of applications, such as radio transmitters, radars, and electronic ballasts. When the frequency of oscillations is required to be accurate and stable, crystal oscillators are used. In these oscillators, the oscillation frequency is precisely controlled by the vibrations of a quartz crystal. The crystal is a mechanical resonator. Electronic watches and other critical timing applications use crystal oscillators because they provide an accurate ...