Nowadays Electronics become the important part of our day to day life. Most of the gadgets and control circuits are designed using basic electronic devices. People are taking interest in this subject either as hobby or a career. This book will explain the basic construction and working of basic devices used in electronics. The text in this book is also useful to students preparing for B.Sc., diploma, degree and other engineering examinations.The simple language and the lecture style used by the author makes the reader to understand the subject very easily. The author has given focus on concepts rather than mathematical derivations. These features will help the reader to understand the theoretical and practical use of electronic devices.