Basic electronics is a compulsory subject for the first year engineering students from all the disciplines. This book is primarily intended to serve as a textbook in accordance with the syllabus of Basic Electronics offered by various universities in India. It also meets the needs of those readers who want to gain a sound understanding of the principles of electronics. This book has been written in a very simple and lucid manner. Every effort has been made to make the treatments simple and comprehensive. Throughout the book, the stress has been given on fundamental concepts through illustrative examples. Neat and clear diagrams have been used for explanation. A large number of self explanatory accurate diagrams and tables have been used to supplement the text. Exercises and problems are also provided. This will help the students to prepare accordingly. This book is also intended as a textbook for the use in Electronics and Communication courses in polytechnics, IETE, AMIE and for various Engineering Electronics examinations. Thus, primarily designated as an undergraduate textbook for students of science and technology, this study will provide balanced coverage of devices, analog and digital circuits, with an emphasis on analog electronics. I have no claim to the original research in preparing this book. Liberal use of the materials available in the work of eminent authors has been made. I have tried to fashion the vast amount of material available from primary and secondary sources into coherent body of description and analysis. Errors might have crept in despite utmost care to avoid them and author shall be grateful if these are reported along with other suggestions for improvement of the book.