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Review of Mancini: Op Amps For Everyone

Download Op Amps for Everyone (pdf) from Texas Instruments

Well, maybe it should be called Op Amps for Almost Everyone. If you are new to electronics, then the very gentle introduction in the Operational Amplifiers chapter of Lessons In Electric Circuits (allaboutcircuits) by Kuphaldt might better suit your needs. However, as you gain more knowledge in electronics, make sure to come back to Mancinis fine book. It has much more depth than Kuphaldts basic introduction, both in the theoretical chapters and in the practical advice. It is enormously popular. When someone asks on any electronics forum where he can learn about Operational Amplifiers (Op Amps), most of the time people will refer him to this free book. For an even more advanced treatment of Op Amps, take a look at Jung.

If you like the book and plan to use it often, you might consider to buy the 3rd edition of Op Amps for Everyone. Some typos have been removed and several chapters have been added. By the way, Mancini has also written the very interesting Analog Angle columns for EDN.

In fact, it covers more than just Op Amps. If you are new to Op Amps and you just want to learn the most important things about them, I suggest you focus on the following chapters:
-Review of Circuit Theory (if you need it)
-Development of the Ideal Op Amp Equations
-Feedback and Stability Theory (in particular, make sure that you understand the meaning of the Bode plots)
-Development of the Non Ideal Op Amp Equations
-Voltage-Feedback Op Amp Compensation (this may save you from the embarrassing situation where an amplifier that you designed turns into an oscillator. Again, most important is that you understand the Bode plots)
-Op Amp Noise Theory and Applications
-Understanding Op Amp Parameters

Mancini suggests an order that is a bit different (in the 2nd paragraph of the foreword): The novice reader should first read chapters 1 through 9. However, I think that the reader who is new to Op Amps should ignore the Current Feedback (CFB) Op Amp that is treated in chapters 8 and 9 and should focus on the Voltage Feedback (VFB) Op Amp instead (the VFB Op Amp is the normal Op Amp. When people talk about Op Amps without further qualification, they usually mean the VFB). The CFB becomes an interesting choice if someone is dealing with higher frequencies, but that would be a very difficult subject for someone who is new to electronics, regardless of the Op Amp. So unless you already know that you want to specialize in higher frequency circuits, you should first focus exclusively on the VFB.

Here are some comments on the individual chapters in their order: After some remarks on the history of feedback and Op Amps in chapter 1, chapter 2 provides a review of circuit theory. It is nice to read if you already have some knowledge about this topic and this knowledge is a bit rusty. But if you never heard anything about, say, Thevenins Theorem then you may again prefer the long and careful treatment in Kuphaldts book, this time in the DC Network Analysis chapter. Or have a look at one of the other resources on basic linear circuit analysis.

Chapter 3 covers the equations of the ideal Op Amp, this is the most fundamental knowledge you need to have about Op Amps.

The design technique for single supply Op Amps that is presented in chapter 4 I found somehow strange, maybe I am just too stupid to properly understand it. But the Single Supply Circuit Collection in Appendix A is very useful. In any case, if you are new to Op Amps, maybe you should defer the study of Single Supply Op Amps until later.

Chapter 5 about Feedback and Stability Theory may at first appear to be a bit difficult for the novice, but you should at least try to work through it, it is extremely important. If you do not understand every detail of the block diagrams at the begin of the chapter, do not worry. The most important thing are the Bode Plots starting at section 5.4. They are the key to understanding stability. Once you mastered them, they are a vary valuable and intuitive tool. They are used extensively in chapter 7 about Op Amp compensation. As Mancini explains, a good understanding of this topic is not only important to avoid unwanted oscillations (this would be the worst outcome), but also unwanted results like ringing.

Chapters 8 and 9 are about Current Feedback (CFB) Op Amps and a comparison between them and the more common Voltage Feedback (VFB) Op Amps. CFB are most important if you want to design high frequency circuits.

Chapter 10 covers Op Amp Noise Theory and Applications. It is also a very readable general introduction to noise, the different kinds of noise are cleary explained.

Chapter 11 provides a good overview of the different parameters that characterize an Op Amp. Of course it follows the terminology used at Texas Instruments, so if you see a data sheet from another manufacturer, names and abbreviations might differ. The best part of the chapter are the good explanations of the most important parameters in section 11.3. If you study them carefully, you are in a good position to fully understand an Op Amps data sheet, and this can save you from nasty surprises.

Chapters 12 to 16 cover several important applications of Op Amps: Signal conditioning of sensor signals, applications of high speed Op Amps in wireless communication systems, buffer Op Amps for D/A converters, using Op Amps to build oscillators and active filters. You do not have to read all of them, but it will certainly expand your knowledge about Op Amps if you look at some typical applications of them. Just chose the topic that interests you most. You can find even more of them on the Op Amp Applications page.

Chapter 17 about Circuit Board Layout Techniques gives very important and practical advice. It teaches you how to look at the circuit board as an electrical component which can be just as important for the proper function of your circuit as resistors and capacitors.You do not have to read it if you are just interested in understanding Op Amps, but if you actually have to build any kind of production circuits (with Op Amps or not) using a printed circuit board (PCB) instead of just building a prototype you should study it very carefully.

Chapter 18 teaches you how to design Low Voltage Op Amp Circuits. As long as you design your circuits just for the laboratory, access to a +-15 V power supply should not be a problem and you do not have to worry much about low voltage or single supply op amp circuits. However, if you plan to build transportable devices for the real world, power supply by a (preferably small) battery becomes a key issue and you should study this chapter carefully (and also the single supply circuit collection in Appendix A).

You should also take a look at some recommendations for other books on Op Amps. The other free E-books and Application Notes from Texas Instruments are also very interesting.

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