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. Though present day electronics is dominated by linear and digital integrated circuits, the importance of discrete devices cannot be undervalued as they continue to be used in large numbers in a variety of electronic circuits. In addition, understanding operational basics of these devices makes it easier to understand more complex integrated circuits. This textbook covers electronic devices and circuits in entirety, for undergraduate and graduate level courses. This study is pertinent for students of electronics, electrical, communication, instrumentation and control, information technology and even computer science engineering.