This part is a kind of semiconductor called ARF473.

Function of this product has N-channel Enhancement MODE Power MOSFETs.

Manufacturers : Advanced Power Technology

Image and pinout :

Some of the text within the PDF file :

Common Source Push-Pull Pair D G ARF473 AR S (Flange) D F47 3 RF POWER MOSFET N - CHANNEL ENHANCEMENT MODE • Specified 135 Volt, 130 MHz Characteristics: • Output Power = 300 Watts. • Gain = 13dB (Class AB) • Efficiency = 50% MAXIMUM RATINGS Symbol VDSS ID VGS PD TJ,TSTG TL Parameter Drain-Source Voltage Continuous Drain Current @ TC = 25°C Gate-Source Voltage Total Device Dissipation @ TC = 25°C Operating and Storage Junction Temperature Range Lead Temperature: 0.063" from Case for 10 Sec. (each device) G 165 V 300 W 150 MHz The ARF473 is a matched pair of RF power transistors in a common source configuration. It is designed for high voltage push-pull or parallel operation in narrow band ISM and MRI power amplifiers up to 150 MHz. • High Performance [ ... ]

ARF473 PDF Datasheet Download