This is an excellent book if you have a good theoretical background in electronics (especially analog electronics) but have not much practical experience in designing real circuits. It will quickly teach you a lot of the things that you need to know if you want to design a circuit that can be successfully produced in volume. The book contains a lot of detailed and practical information but is very easy on the math and very readable.
If you are new to electronics this book is not for you - take a look at Practical Electronics for Inventors or the free e-book Lessons In Electric Circuits (allaboutcircuits) instead. The author makes no attempt to review the basics of electronics, he assumes that you already know them. He tells you about the most important problems that you may encounter in the real world and how you can avoid them. He starts with something that looks so trivial on a schematic, but can cause much headache in a real circuit: Ground. The author clearly explains everything that can happen at such a place where one would (naively) assume that it is always at 0 V. The next section is about something that is, (in theory) equally trivial: Wires and Cables. The author not only discusses the issues you have to consider when you move to higher frequencies (this you will find in many books because it is an interesting application of electromagnetic theory), but also the relevant standards for such a seemingly simple thing as a mains power cable (such things are ignored by most authors, but cannot be ignored by you if you want to sell your product).
The next chapter contains a very good discussion about printed circuit boards. It contains every detail about PCBs that you can think of, plus a section that will help you to decide between SMD and through hole. Then one chapter about passive components, again with an incredible amount of most valuable details, one about active components and a chapter about analog ICs with a focus on Op Amps. As in the other chapters of the book you can find a lot of information that is hard to get from other sources and clearly shows the authors experience. For example, most books that cover the parameters of real Op Amps will tell you about slew rate. But Williams also discusses what consequences it will have if positive and negative slew rate differ.
There is also a chapter about digital circuits. But the focus is on the analog aspects that have to be considered even in digital circuits, like noise immunity and decoupling. The following chapter is about power supplies. The last two chapters are about EMC and general product design.
The book is clearly focused on the needs of the (new) design engineer who has to take into account such aspects as safety, reliability, testability, conformance to standards, availability of components and economic considerations to design a circuit that is ready for production in (high) volume. If your focus is more on building single circuits for your own needs in the laboratory, it will be less useful to you, and a book like the The Art of Electronics might better suit your needs.
No single book can tell you everything you need to know to avoid problems with real word circuits. But this book contains a very good selection of the most important topics. I think it can be extremely helpful for starting a career as a design engineer, especially if your focus is on analog electronics. By the way, another very interesting (and free !) book that will help you to quickly acquire practical knowledge about analog circuit design is ANALOG SEEKrets by Green.
You should also take a look at some recommendations for other books on practical analog electronics.
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