OVERVIEW

Though amplification might appear as a rather limited form of signal processing, it is nevertheless of fundamental importance because most other signal processing circuits are implemented using amplifiers as basic ingredients. Until a few decades ago, an engineer who needed an amplifier had to design it from scratch, using dozens of assorted components such as resistors, capacitors, diodes, and transistors, not to mention endless slide-rule calculations. Mercifully, it turns out that a considerable portion of this circuitry is common to a wide variety of amplifiers. To simplify amplifier design, integrated-circuit manufacturers provide this common circuitry as a ready-made universal building block. Then, with the help of only a few external components, the user personalizes this block to the particular application at hand.

Surprisingly, this building block is itself an amplifier. Called an operational amplifier, or op amp for short, it is fabricated on a miniature silicon chip and is made available as an off-the-shelf component. In mass production, its cost may be comparable to that of individual circuit elements such as resistors, transistors, and potentiometers. The combination of low cost, miniature size, high reliability, and easy use makes the op amp the most popular device in analog circuit design.

In this chapter, after introducing op amp models and terminology, we examine the most basic op amp configurations, that is, the noninverting, inverting, and buffer amplifiers. In so doing, we introduce another cornerstone concept of electrical engineering, namely, the concept of negative feedback.