Phase-lock basics | This is the second edition of a book about the basics of phase-locked loops (PLLs). Basics tend to be unchanging, but we can learn more about them and their manner of presentation can be improved and tuned to current practice. Loop filters driven by current sources are now so common that I have given them a more prominent place, allowing them to lead into the study of filters that use op-amps, rather than the reverse. The discussion of various applications, at the end of Part 1, which is designed to show how the basics can be applied to a wide variety of circuits, as well as to broaden the overview, has been expanded to include the now common use of PLLs for timing adjustment in ICs. This discussion includes the delay-locked loop, which is not a PLL but whose common forms can still be analyzed with the basic techniques that are used for PLLs. Frequency synthesis is another important application to which the basics can be applied, and I have broadened that description by adding material on modern fractional-N and sigma–delta techniques.
