This part is a kind of semiconductor called BD243.

Function of this product has Medium Power Linear and Switching Applications.

Manufacturers : Fairchild Semiconductor

Image and pinout :

Some of the text within the PDF file :

BD243/A/B/C BD243/A/B/C Medium Power Linear and Switching Applications • Complement to BD244, BD244A, BD244B and BD244C respectively 1 TO-220 2.Collector 3.Emitter 1.Base NPN Epitaxial Silicon Transistor Absolute Maximum Ratings TC=25°C unless otherwise noted Symbol VCBO Parameter Collector-Base Voltage : BD243 : BD243A : BD243B : BD243C VCEO Collector-Emitter Voltage : BD243 : BD243A : BD243B : BD243C Emitter-Base Voltage Collector Current (DC) *Collector Current (Pulse) Base Current Collector Dissipation (TC=25°C) Junction Temperature Storage Temperature 45 60 80 100 45 60 80 100 5 6 10 2 65 150 - 65 ~ 150 V V V V V V V V V A A A W °C °C Value Units VEBO IC ICP IB PC TJ TSTG Electrical Characteristics TC=25°C unless otherwise noted Symbol VCEO(sus) Parameter * Collector-Emi [ ... ]

BD243 PDF Datasheet Download