Understanding basic operational and applications of electronic devices is fundamental in understanding the functional and design aspects of electronics techniques, sub system or system irrespective of whether it is analog or digital. The study of electronics devices and circuits is essential since majority of electronics systems have both analog and digital content. The book Basic Electronic Devices and Circuits is primarily for diploma, Degree and other Engineering examinations. It will also meet the needs of those readers who wish to gain sound knowledge of electronics. The purpose of this book is to provide a comprehensive and up-to-date study. The book uses a plain, lucid and everyday language to explain the subject matter. The entire content in the book is provided in a logical, orderly and a self-understandable manner. The book prepares very carefully a background of each topic with essential illustration and diagrams.