A BC817 transistor is a negative-positive-negative (NPN) transistor that is used for many purposes. 

 A transistor is a semiconductor device used to amplify and switch electronic signals and electrical power.

Transistor Type - NPN

Collector Voltage    - 45v

DC Current              - 500mA

Transistor               - SOT-23

Transistor Pins      - 3 Pin

Max. Temp.             - 150°C