Transistor: NPN; bipolar; 400V; 1A; 40W; TO220

A bipolar transistor is a three-layer semiconductor device that can amplify signals or act as a switch. An NPN transistor has a p-doped base between two n-doped regions and conducts current from the collector (C) to the emitter (E) when a small current is applied to the base (B). The TO220 package is a widely used type for through-hole mounting of powerful semiconductor devices, consisting of a metal plate for heat dissipation and three wires for electrical connection.