The Textbook section of All About Circuits hosts Lessons in Electric Circuits, a free electronics textbook by Tony R. Kuphaldt. It is organized in volumes on DC circuits, AC circuits, semiconductors, digital circuits and a reference volume.
Each volume moves from basic concepts such as voltage, current, resistance and the fundamental circuit laws to network analysis, filters, transistors, operational amplifiers and logic gates, with worked examples and explanatory diagrams. Chapters are short and can be read as a reference for a single topic.
The book is published under an open license and can be read online without registration. It is a solid foundation for engineers from other disciplines who need to understand circuits, but it is a textbook and offers no simulator or calculator for design work.
