This book is useful for Under Graduated Students. In 1st Unit, it describes the Basic Concepts of Electronics, PN Junction Diodes, Zener Diodes and its Applications. In 2nd Unit, it describes the Bipolar Junction Transistor, its Operations, Applications, as well as different Biasing Techniques. In 3rd Unit, it describes the Field Effect Transistors and Its Applications. In 4th Unit, it describes the Operational Amplifier, Different Configurations and Different Applications of it.