At frequencies under 1 MHz, we can use RC oscillators to produce
almost perfect sine waves. These low-frequency oscillators use op amps
and RC resonant circuits to determine the frequency of oscillation.
Above 1 MHz, LC oscillators are used. These high-frequency oscillators
use transistors and LC resonant circuits. This chapter also discusses a
popular chip called the 555 timer. It is used in many applications to
produce time delays, voltage-controlled oscillators, and modulated
output signals. The chapter also covers an important communications
circuit called the phase-locked loop (PLL) and concludes with the
popular XR-2206 function generator IC.
