Description: After studying this lesson, you should be able to learn about, energy bands are and how they are used to classify materials as conductors, insulators and semiconductors, intrinsic semiconductors and extrinsic semiconductors, n-type semiconductors and p-type semiconductors, formation of depletion region and barrier potential in a p-n junction diode, I-V characteristics of a p-n junction diode in the forward and reverse biases, different type of diodes, viz. zener, LED, photo diode and solar cell and their I-V characteristics, the action of a transistor, the effect of doping, size and function of different regions in a transistor, differences between p-n-p and n-p-n transistors, different configurations in which a transistor can be connected and describe their input and output characteristics, compare different configurations of a transistor in terms of their input/output resistance, gain and applications