Pinout drawing of a TIP-120 transistor. From left to right the legs are labelled 1. base, 2. collector, 3. emitter.
Pinout drawing of a TIP-120 transistor. It is facing forward with the heat sink tab at the top and the bulging side of the component facing you. From left to right the legs are labelled 1. base, 2. collector, 3. emitter.