This part is a kind of semiconductor called BC817-25.

Function of this product has NPN Small Signal Transistor.

Manufacturers : Micro Commercial Components

Image and pinout :

Some of the text within the PDF file :

MCC TM Micro Commercial Components
  omponents 20736 Marilla Street Chatsworth    !"# $ %    !"# Features • Halogen free available upon request by adding suffix "-HF" • Lead Free Finish/RoHS Compliant ("P" Suffix designates RoHS Compliant. See ordering information) • Epoxy meets UL 94 V-0 flammability rating • Moisure Sensitivity Level 1 • Ideally Suited for Automatic Insertion • 150 C Junction Temperature • For Switching and AF Amplifier Applications • Epitaxial Planar Die Construction Mechanical Data • Case: SOT-23, Molded Plastic • Terminals: Solderable per MIL-STD-202, Method 208 • Polarity: See Diagram • Weight: 0.008 grams ( approx.) • Marking: BC817-16 6A BC817-25 6B BC817-40 6C Maximum Rat [ ... ]

BC817-25 PDF Datasheet Download