Chapter Outline

14.1 Introduction

14.2 Differential and Common-Mode Operation

14.3 Op-Amp Basics

14.4 Practical Op-Amp Circuits

14.5 Op-Amp Specifications DC Offset Parameters

14.6 Op-Amp Specifications Frequency Parameters

14.7 Op-Amp Unit Specifications

14.8 PSpice Windows

Learning Outcomes

After completing this chapter you will be able to:

- Explain the difference between common mode and differential mode operation

- Explain the operation of the basic op-amp

- Calculate the output voltage for a number of basic op-amp configurations

- Explain the terminology associated with the dc and ac performance of an op-amp

- Interpret manufacturers specification to determine op-amp performance


An operational amplifier, or op-amp, is a very high gain differential amplifier with high input impedance and low output impedance. Typical uses of the operational amplifier are to provide voltage amplitude changes (amplitude and polarity), oscillators, filter circuits, and many types of instrumentation circuits. An op-amp contains a number of differential amplifier stages to achieve a very high voltage gain.

Figure 14.1 shows a basic op-amp with two inputs and one output as would result using a differential amplifier input stage. Recall from Chapter 12 that each input results in either the same or an opposite polarity (or phase) output, depending on whether the signal is applied to the plus (+) or the minus () input. fig14_1.gif


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