CHAPTER TWELVE
Phase-Lock Loops
12.1 INTRODUCTION
Phase-lock loops (PLL) became widespread with the availability of high-quality integrated circuit operational amplifiers (op-amps) in the 1960s. Since then this versatile circuit has found applications across the frequency spectrum in consumer, commercial, deep space, and military projects. Understanding the operation of the PLL incorporates RF techniques, oscillator design, closed-loop control theory, analog circuit design, and digital circuit design. The references listed at the end of this chapter provide insight beyond the present scope [1–4]. This chapter begins with the basic concepts, which are later expanded into practical designs.
12.2 PLL DESIGN BACKGROUND
The PLL uses negative feedback to tailor its performance. The primary design parameters are response time, transient performances, bandwidth, damping ratio, and phase margin. The type and order of a closed-loop system define the complexity and response to a stimulus. At least two of the components of a PLL, the voltage-controlled oscillator (VCO) and the phase detector, are high-frequency components. There may also be amplifiers, mixers, frequency multipliers, and other oscillators that require RF techniques.
Many integrated circuits are presently available that combine many of the PLL functions on a single chip. Operational amplifiers often are used in filter circuits, which may be either inverting or noninverting designs as required by the phase-lock loop design. Integrators, ...
