This part is a kind of semiconductor called BD137.
Function of this product has NPN power transistors.
Manufacturers : NXP
Image and pinout :
Some of the text within the PDF file :
DISCRETE SEMICONDUCTORS DATA SHEET book, halfpage M3D100 BD135; BD137; BD139 NPN power transistors Product speciﬁcation Supersedes data of 1997 Mar 04 1999 Apr 12 Philips Semiconductors Product speciﬁcation NPN power transistors FEATURES • High current (max. 1.5 A) • Low voltage (max. 80 V). APPLICATIONS • Driver stages in hi-fi amplifiers and television circuits. DESCRIPTION NPN power transistor in a TO-126; SOT32 plastic package. PNP complements: BD136, BD138 and BD140. handbook, halfpage BD135; BD137; BD139 PINNING PIN 1 2 3 emitter collector, connected to metal part of mounting surface base DESCRIPTION 2 3 1 1 2 3 Top view MAM254 Fig.1 Simplified outline (TO-126; SOT32) and symbol. LIMITING VALUES In accordance with the Absolute Maximum Rating System (IEC 134) [ ... ]