This part is a kind of semiconductor called BD157.

Function of this product has Plastic Medium Power NPN Silicon Transistor.

Manufacturers : Motorola Inc

Image and pinout :

Some of the text within the PDF file :

MOTOROLA SEMICONDUCTOR TECHNICAL DATA Order this document by BD157/D Plastic Medium Power NPN Silicon Transistor . . . designed for power output stages for television, radio, phonograph and other consumer product applications. • Suitable for Transformerless, Line–Operated Equipment • Thermopad{ Construction Provides High Power Dissipation Rating for High Reliability MAXIMUM RATINGS Rating BD157 BD158 BD159 0.5 AMPERE POWER TRANSISTORS NPN SILICON 250 – 300 – 350 VOLTS 20 WATTS ÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎ ÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎ ÎÎÎÎÎÎÎÎÎÎÎ ÎÎÎÎ ÎÎÎ ÎÎÎÎ ÎÎÎ ÎÎÎ ÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎ ÎÎÎÎÎÎÎÎÎÎÎ ÎÎÎÎ ÎÎÎ ÎÎÎÎ ÎÎÎ ÎÎÎ ÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎ [ ... ]

BD157 PDF Datasheet Download