BC517 is an NPN bipolar transistor from CDIL. It has Darlington configuration and is capable of handling 30V and 1A of current. Its power dissipation is rated at 625mW and it comes in a TO92 package. It is becoming increasingly popular for its excellent switching performance, low noise, and low saturation voltage. It is also used for telecommunication circuits, amplifiers, and switching circuits, in combination with other transistors such as the BC547, BC548, and BC549.