This part is a kind of semiconductor called BD243C.

Function of this product has Complementary Silicon Plastic Power Transistors.

Manufacturers : ON Semiconductor

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Some of the text within the PDF file :

BD243B, BD243C (NPN), BD244B, BD244C (PNP) Complementary Silicon Plastic Power Transistors These devices are designed for use in general purpose amplifier and switching applications. Features • High Current Gain Bandwidth Product • These Devices are Pb−Free and are RoHS Compliant* MAXIMUM RATINGS Rating Symbol Value Unit Collector−Emitter Voltage BD243B, BD244B BD243C, BD244C VCEO 80 100 Vdc Collector−Base Voltage BD243B, BD244B BD243C, BD244C VCB Vdc 80 100 Emitter−Base Voltage Collector Current − Continuous Collector Current − Peak Base Current Total Device Dissipation @ TC = 25°C Derate above 25°C VEB 5.0 Vdc IC 6 Adc ICM 10 Adc IB 2.0 Adc PD 65 W 0.52 W/°C Operating and Storage Junction Temperature Range TJ, Tstg −65 to +150 °C Stresses exceeding [ ... ]

BD243C PDF Datasheet Download