This part is a kind of semiconductor called FB42N20D.

Function of this product has IRFB42N20D.

Manufacturers : International Rectifier

Image and pinout :

Some of the text within the PDF file :

PD- 94208 SMPS MOSFET IRFB42N20D HEXFET® Power MOSFET Applications High frequency DC-DC converters l Motor Control l Uninterrutible Power Supplies l VDSS 200V RDS(on) max 0.055Ω ID 44A Benefits l Low Gate-to-Drain Charge to Reduce Switching Losses l Fully Characterized Capacitance Including Effective COSS to Simplify Design, (See App. Note AN1001) l Fully Characterized Avalanche Voltage and Current Absolute Maximum Ratings Parameter ID @ TC = 25°C ID @ TC = 100°C IDM PD @TA = 25°C PD @TC = 25°C VGS dv/dt TJ TSTG Continuous Drain Current, VGS @ 10V Continuous Drain Current, VGS @ 10V Pulsed Drain Current  Power Dissipation Power Dissipation Linear Derating Factor Gate-to-Source Voltage Peak Diode Recovery dv/dt ƒ Operating Junction and Storage Temperatu [ ... ]

FB42N20D PDF Datasheet Download