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Recommendations for Bipolar Junction Transistor Resources

On this page you can find several resources about Bipolar Junction Transistors (BJTs). There exist several other types of transistors (e.g. MOSFETs), but the BJT is a good general purpose transistor if you want to understand and build analog electronic circuits. If you are especially interested in the semiconductor foundations of BJTs you should also have a look at the page on Diodes - once you have understood the single pn junction of a diode, understanding how BJTs work will become easier. If you do not only want to understand how a single transistor works, but you also want to build and analyze more complex circuits that use transistors, you might also want to look at the resources in analysis and design of electronic circuits. Finally one general advice if you are learning about electronics on your own and you are free to choose the order in which you cover the different topics: You should consider to learn about Op Amps as the basic building block of analog electronics before you learn about transistors. The basic operation of a BJT is relatively easy to understand. But before you can use it to build real circuits, you have to learn some tricks to compensate for its very nonlinear behavior. Analyzing transistor circuits is difficult unless you have some experience and you know which approximations you have to use. Circuits using operational amplifiers are much easier to analyze. This does not mean that learning about transistors is less important - among other things, a thorough understanding of transistors is indispensable if you want to understand the finer details of operational amplifiers. You should just think about which order of topics is best for you.

A very good place to start learning about BJTs is the free chapter on BJTs in allaboutcircuits by Kuphaldt. You should not be afraid of the warning signs that the pages require proofreading - this is mostly about minor grammar errors. If you find an error (or suspect that something is wrong) you can report it in the Feedback and Suggestions forum and you will usually receive a quick answer. After you have read through the chapter you should try to solve the BJT problems in socratic electronics by the same author (take a look at the "Discrete semiconductor devices and circuits" section). Some of the problems are quite advanced, and sometimes you might not completely understand the answers. In this case (or if there is anything you did not understand in the BJT chapter) you should not hesitate to register at the allaboutcircuits forum and ask your question there - the correct subforum is the General Electronics Chat.

Moving forward faster than Kuphaldt, but still relatively easy to understand, are the Transistor Pages of Storr's Basic Electronics Tutorials. Pages 1 to 4 cover bipolar transistors, on page 8 is a comparison between bipolar and field effect transistors.

You can find a very good and advanced treatment (but still with a minimum of mathematics) of BJTs in chapter 2 (p.61 -111) of The Art of Electronics by Horowitz and Hill (chapter 3 covers JFETs and MOSFETs). The chapter starts with a very simplified transistor model and a discussion of some basic topics like emitter followers, common emitter amplifiers, biasing and using BJT transistors to build voltage and current sources. Then the authors introduce the Ebers Moll model and use it as the foundation for the discussion of all following circuits. Current mirrors, class A, B and AB amplifiers, the Darlington configuration, differential amplifiers and the Miller effect are discussed. One point that the authors emphasize is that you should not rely on a particular value of the current gain (called beta or hfe) of a BJT. You should have a look at figure 2.78, p.106. If you compare this wide spread of beta with, say, the 5% tolerance that you can very easily obtain for a resistor, it is quite shocking. You might wonder how it is possible at all to build transistor circuits with a specified performance. But don't worry, the authors explain to you the circuits that are relatively independent of the particular value of beta (and also those that should be avoided because their performance will vary too much). In Chapter 7 on Precision Circuits and Low Noise Techniques, noise in transistor amplifiers is explained for BJTs and JFETs (p. 436- 445). In chapter 13 on High Frequency and High-Speed Techniques transistors are discussed on p. 863 - 873 and p.905 - 913.

A good (and free) resource that "emphasizes fast rough methods of analysis (analysis by inspection)" is Professors Notes BJT Circuit Analysis by Ray Winton, Mississipi State University.

In Sedra / Smith you can find a very comprehensive treatment of transistors and the circuits that you can build with them, together with lots of examples, exercises and problems. BJTs are covered in chapter 6, p.350 - 489.

You can find some details about the semiconductor foundations of BJTs in Sodinis free lecture notes Microelectronic Devices and Circuits (MIT Open Course Ware), lectures 17 and 18.

If you have questions about BJT transistors you can ask them in the Physics Forums: For general questions in the Electrical Engineering subforum and for homework questions in the Homework / Engineering or the Homework / Introductory Physics subforum.

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