This part is a kind of semiconductor called FDT3N40.

Function of this product has MOSFET.

Manufacturers : Fairchild Semiconductor

Image and pinout :

Some of the text within the PDF file :

FDT3N40 N-Channel UniFETTM MOSFET FDT3N40 N-Channel UniFETTM MOSFET 400 V, 2.0 A, 3.4 Features • RDS(on) = 3.4 Ω (Max.) @ VGS = 10 V, ID = 1.0 A • Low Gate Charge (Typ. 4.5 nC) • Low Crss (Typ. 3.7 pF) • 100% Avalanche Tested Applications • LCD/LED TV • Lighting • Uninterruptible Power Supply April 2013 Description UniFETTM MOSFET is Fairchild Semiconductor®’s high voltage MOSFET family based on planar stripe and DMOS technology. This MOSFET is tailored to reduce on-state resistance, and to provide better switching performance and higher avalanche energy strength. This device family is suitable for switching power converter applications such as power factor correction (PFC), flat panel display (FPD) TV power, ATX and electronic lamp ballasts. D S G SOT-223 Absolute [ ... ]

FDT3N40 PDF Datasheet Download