COMPUTING

Chapter 5Operational AmplifiersThis chapter begins with an introduction to operational amplifiers (op amps), characteristics,and applications. We will discuss the ideal op amp, analysis of circuits in the inverting andnon−inverting configurations, and gain and bandwidth on circuit performance. We will alsointroduce some circuits consisting of op amps and non−linear devices, and analog computers.5.1 The Operational AmplifierThe operational amplifier or simply op amp, is the most versatile electronic amplifier. It derives itname from the fact that it is capable of performing many mathematical operations such as addition,multiplication, differentiation, integration, and analog−to−digital conversion or vice versa. Itcan also be used as a comparator and electronic filter. It is also the basic block in analog computerdesign. Its symbol and pinouts are shown in Figure 5.1.23−+V +7V −46Figure 5.1. Symbol and pinouts for operational amplifierAs shown above the op amp has two inputs but only one output. For this reason it is referred to asdifferential input, single ended output amplifier. Figure 5.2 shows the internal construction of thepopular 741 op amp. This figure also shows terminals V + and V − . These are the voltage sourcesrequired to power up the op amp. Typically, V + is +15 volts and V − is −15 volts. These terminalsare not shown in op amp circuits since they just provide power, and do not reveal any other usefulinformation for the op amp’s circuit analysis.5.2 An Overview of the Op AmpThe op amp has the following important characteristics:1. Very high input impedance (resistance)2. Very low output impedance (resistance)3. Capable of producing a very large gain that can be set to any value by connection of externalresistors of appropriate valuesElectronic Devices and Amplifier Circuits with MATLAB Computing, Second EditionCopyright © Orchard Publications5−1