This part is a kind of semiconductor called BUK108-50GS.
Function of this product has PowerMOS transistor TOPFET.
Manufacturers : NXP
Image and pinout :
Some of the text within the PDF file :
Philips Semiconductors Product specification PowerMOS transistor TOPFET DESCRIPTION Monolithic temperature and overload protected power MOSFET in a 3 pin plastic surface mount envelope, intended as a general purpose switch for automotive systems and other applications. BUK108-50GS QUICK REFERENCE DATA SYMBOL VDS ID PD Tj RDS(ON) PARAMETER Continuous drain source voltage Continuous drain current Total power dissipation Continuous junction temperature Drain-source on-state resistance VIS = 10 V MAX. 50 15 40 150 100 UNIT V A W ˚C mΩ APPLICATIONS General controller for driving lamps motors solenoids heaters FEATURES Vertical power DMOS output stage Low on-state resistance Overload protection against over temperature Overload protection against short circuit load Latched overload prot [ ... ]