This part is a kind of semiconductor called 2N5551S.

Function of this product has EPITAXIAL PLANAR NPN TRANSISTOR.

Manufacturers : KEC

Image and pinout :

Some of the text within the PDF file :

SEMICONDUCTOR TECHNICAL DATA GENERAL PURPOSE APPLICATION. HIGH VOLTAGE APPLICATION. FEATURES High Collector Breakdwon Voltage : VCBO=180V, VCEO=160V Low Leakage Current. : ICBO=50nA(Max.) VCB=120V Low Saturation Voltage : VCE(sat)=0.2V(Max.) IC=50mA, IB=5mA Low Noise : NF=8dB (Max.) MAXIMUM RATING (Ta=25 ) CHARACTERISTIC SYMBOL RATING Collector-Base Voltage VCBO 180 Collector-Emitter Voltage VCEO 160 Emitter-Base Voltage VEBO 6 Collector Current IC 600 Base Current IB 100 Collector Power Dissipation PC * 350 Junction Temperature Tj 150 Storage Temperature Range Tstg -55 150 Note : * Package Mounted On 99.5% Alumina 10 8 0.6 ) UNIT V V V mA mA mW 2N5551S EPITAXIAL PLANAR NPN TRANSISTOR E L BL DIM MILLIMETERS A 2.93+_ 0.20 B 1.30+0.20/-0.15 A G H D 23 C 1.30 MA [ ... ]

2N5551S PDF Datasheet Download