A transistor is a semiconductor device used for amplification and switching applications in electrical and electronic circuits. It consists of three regions: emitter, base, and collector. The transistor action is based on the principle of controlling the flow of current between collector and emitter using a small input current at the base. A transistor usually has two types: NPN and PNP, which differ in the arrangement of semiconductor layers and direction of current flow. In an NPN transistor, a thin p-type base is sandwiched between two n-type regions, whereas in a PNP transistor, an n-type base is sandwiched between two p-type regions. The working of a transistor can be explained by considering the NPN transistor. When the emitter-base junction is forward biased and the base-collector junction is reverse biased, transistor action occurs. The emitter is heavily doped to supply charge carriers, while the base is lightly doped and very thin to allow most carriers to pass through to the collector. The collector is moderately doped and is designed to collect carriers efficiently. When a small base current is applied, it controls a much larger collector current, enabling amplification. In transistor