PREFACE

What is the value of pi (π)? Is it 3? Is it 3.1? How about 3.14? Or perhaps you think 3.1415952653589793238462643383279 is more appropriate. Each of these answers is correct just as each of these answers is incorrect; they vary in their degrees of resolution and accuracy. The degree of accuracy is often proportional to the complexity or difficulty of computation. So it is with operational amplifier circuits, or all electronic circuits for that matter. The goal of this text is to provide workable tools for analysis and design of operational amplifier circuits that are free from the shrouds of complex mathematics and yet produce results that have a satisfactory degree of accuracy.

This book offers a subject coverage that is fairly typical for texts aimed at the postsecondary school market. The organization of each circuits chapter, however, is very consistent and provides the following information on each circuit presented:

In addition to presenting these areas for each type of circuit, each circuits chapter has a discussion of troubleshooting techniques as they apply to the type of circuits discussed in that particular chapter.

The majority of this text treats the op amp as a quasi-ideal device. That is, only the nonideal parameters that have a significant impact on a particular design are considered. Chapter 10 offers a more thorough discussion of nonideal behavior and includes both AC and DC considerations.

The analytical and design methods provided in the text are not limited to a particular op amp. The standard 741 and its higher-performance companion, the MC1741SC, are frequently used as example devices because they are still used in major electronics schools. However, the equations and methodologies directly extend to newer, more advanced devices. In fact, because newer devices typically perform closer to the ideal op amp, the equations and methods frequently work even better for the newer op amps. To provide a perspective regarding the range of op amp performance that is available, Chapter 11 includes a comparison between a general-purpose op amp and a hybrid op amp, which has for example, a 5500 volts-per-microsecond slew rate as compared to the 0.5 volts-per-microsecond slew rate often found in general-purpose devices.

Every circuit in every circuits chapter has been constructed and tested in the laboratory. In the case of circuit design examples, the actual performance of the circuit was captured in the form of oscilloscope plots. The following test equipment was used to measure circuit performance:

Items 1 to 3 were provided courtesy of Hewlett-Packard. This equipment delivered exceptional ease of use and accuracy of measurement, and produced a camera-ready plotter output of the scope displays. The oscilloscope plots presented in the text are unedited and represent the actual circuit performances, thus alleviating the confusion that is frequently encountered when the ideal waveform drawings typically presented in textbooks are contrasted with the actual results in the laboratory. Any deviations from the ideal that would have been masked by an artist’s ideal drawings are there for your examination in the actual oscilloscope plots presented throughout this book.

Although this text is appropriate for use in a resident electronics school, the consistent and independent nature of the discussions for each circuit make it equally appropriate as a reference manual or handbook for working engineers and technicians.

So what is considered to be a satisfactory degree of accuracy in this text? On the basis of more than 20 years of experience as a technician, an engineer, and a classroom instructor, it is apparent to the author that most practical designs require tweaking in the laboratory before a final design evolves. That is, the engineer can design a circuit using the most appropriate models and the most extensive analysis, but the exact performance is rarely witnessed the first time the circuit is constructed. Rather, the paper design generally puts us close to the desired performance. Actual measurements on the circuit in a laboratory environment will then allow optimization of component values. The methods presented in this text, then, will produce designs that can deliver performance close to the original design goals. If tighter performance is required, then tweaking can be done in the laboratory … a step that would generally be required even if more elaborate methods were employed.

The majority of text material included in the first edition is retained in this second edition. Feedback from reviewers emphasized the point “Take nothing out … it’s all important!” However, all known typographical errors and oversights that appeared in the first edition have been corrected here. We have also updated several references to actual A/D and D/A conversion products in Chapter 8, to identify newer products that are more readily available. Additionally, an instructor’s answer key has been developed and is available from the publisher; it includes solutions to all end-of-chapter problems.

For reasons stated previously, we have elected to continue using the basic 741 as the primary op amp for use in the analysis and design examples. Clearly, the 741 is a mature product, but the analytical techniques presented work well with newer and more ideal op amps. Fortunately, the decision to focus on these older devices to satisfy the requirements of many school curriculums does not lessen the applicability of the material to programs that use higher-performance devices.

Your comments, criticisms, and recommendations for improvement of this text are welcomed. You may send your comments to the publisher; or alternatively, if you prefer you may send your comments directly to the author via e-mail to [email protected]. While visiting the Terrell Technologies, Inc., home page, you can also download other useful educational materials and software products. In early 1996, the company plans to have PSpice files available for all the op amp designs presented in this text; they will be available to be downloaded for free.