This part is a kind of semiconductor called BF989.

Function of this product has N-channel dual-gate MOS-FET.

Manufacturers : NXP

Image and pinout :

Some of the text within the PDF file :

DISCRETE SEMICONDUCTORS DATA SHEET BF989 N-channel dual-gate MOS-FET Product specification File under Discrete Semiconductors, SC07 April 1991 Philips Semiconductors Product specification N-channel dual-gate MOS-FET FEATURES • Protected against excessive input voltage surges by integrated back-to-back diodes between gates and source. APPLICATIONS • UHF applications such as: – UHF television tuners – Professional communication equipment. PINNING PIN 1 2 3 4 SYMBOL s, b d g2 g1 source drain gate 2 gate 1 Top view Marking code: MAp. MAM039 handbook, halfpage BF989 DESCRIPTION Depletion type field-effect transistor in a plastic SOT143 microminiature package with interconnected source and substrate. 4 3 g2 g1 d DESCRIPTION 1 2 s,b Fig.1 Simplified outline (SOT143) and sym [ ... ]

BF989 PDF Datasheet Download