The phase locked loop is a feedback system comprised of a phase comparator, a low pass
filter and error amplifier in the forward signal path and a voltage-controlled oscillator (VC0) in
the feedback path. The block diagram of a basic PLL system is shown. Perhaps the single most
important point to realize when designing with the PLL is that it is a feedback system and, hence,
is characterized mathematically by the same questions that apply to other, more conventional
A communication circuit designer frequently requires means to select (or reject) a band of frequencies from a wide signal spectrum. Resonant circuits provide such ®ltering. There are well-developed, sophisticated methodologies to meet virtually any speci®cation. However, a simple circuit suf®ces in many cases. Further, resonant circuits are an integral part of the frequency-selective ampli®er as well as of the oscillator designs. These networks are also used for impedance transformation and matching.
The operational amplifier ("op amp") is the most versatile and widely used type of analog IC, used in audio and voltage amplifiers, signal conditioners, signal converters, oscillators, and analog computing systems. Almost every electronic device uses at least one op amp. This book is Texas Instruments' complete professional-level tutorial and reference to operational amplifier theory and applications.