Por: Newton C. Braga
Some years ago I had written a book directed to anyone who designs electronic and electric circuits. Engineers, technicians, teachers, students and hobbyists took a real benefit from that book. The original book is now out of print, being available only used issues. Since the book is very useful, the author decided to review the old edition, add new content and so create a new book for anyone who need a fast access to formulas, tables and calculations when designing his projects or solving a problem.
The author, who has himself designed multitudes of projects and circuits during his life, publishing many books and hundreds of articles in electronics magazines and teaching electronics, has collected an assortment of all basic information necessary for calculations needed when designing new projects or solving a problem.
More part of these formulas and calculations is now in the author´s site at www.newtoncbraga.com. The site also has versions in Portuguese (www.newtoncbraga.com.br) and in Spanish (www.incb.com.mx).
In the site the reader will also find practical examples in projects or articles where many of the formulas shown in this book are used.
When starting a project or solving a problem the main difficulty the designer or student founds is how to locate the desired information. This information is normally spread over a large number of resources, such as books, handbooks, Internet, and magazine articles.
Although many of us who are experienced in electronics have in mind the principal formulas, we sometimes have trouble with the forgotten constant, multiplication factor or exponent. Finding these values is sometimes difficult depending of the circumstances, such as where you are at the time or the amount of resources at your disposal.
By putting the principal formulas and tables in a unique place, a designer can find the desired information easier, and, more importantly, can take this information wherever he goes.
And with the aid of the new technologies, the information can be accessed by a tablet, Smartphone or a laptop, if you have the virtual version. This is the aim of this book.
But formulas and tables are not useful only when designing a new configuration. They are necessary when we need to know what happen when a specific working circuit is altered, for the electronic student doing homework or the researchers in other fields who work with electronic equipment.
The tables contain a large amount of important information, such as particular values of constants, physical properties of circuits and materials, and even calculated values that can´t be found without using complex or hard-to-do procedures.
Finally, we have laws and theorems describing the properties of circuits and devices, and procedures to be used in calculations, which are very important when doing practical works.
Most of the formulas and tables are accompanied by application examples. They are very important to show the reader how the calculations are made when using the given information. To avoid problems with incorrect results, in all formulas and applications the units to be used are indicated.
The formulas range from the simplest, where elementary arithmetic operations such as sum, subtraction, multiplication and division, are used, to the more complex that require some good working knowledge of algebraic and trigonometric functions, or even differential and integral calculus.
Although mathematics is an exact science, when some calculations are applied to other sciences and in “real-life” electronics, the results can be different from the expected. When making calculations involving electronic circuits, it is often said that “When working with electronics, practice and theory often disagree.”
This means that in many cases the results found in calculations will need some “adjustments” when applied to an actual application.
This fact is applicable even to the tolerances of the electronic components used in practical applications, plus the fact that many formulas are not exact, but empirical.
But why use an exact formula, including complex logarithms, trigonometric functions or differential equations, if we can get results good enough to make a circuit work by using a reduced formula?
In many stages of the design process, the results will depend on the tolerance of the components used.
This explains why in many cases we´ll not give the exact formula but an empirical formula, where the “complex part” of the calculations will be reduced to a constant, or even eliminated.
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