This part is a kind of semiconductor called STD01P.

Function of this product has Darlington Transistors for Audio Amplifiers.

Manufacturers : Sanken electric

Image and pinout :

Some of the text within the PDF file :

STD01N and STD01P Darlington Transistors for Audio Amplifiers Features and Benefits ▪ Built-in temperature compensation diodes ▪ High power (100 W) handling in a small package (TO-3P), for minimized heat sink requirements ▪ Built-in drivers and temperature compensation diodes, reducing external component count and simplifying circuit design ▪ NPN and PNP versions ▪ Emitter terminals placed symmetrically, pin 5 on NPN and pin 1 on PNP models, allowing adjacent placement on PCB to minimize trace length and output skew when used in pairs ▪ Approved by major manufacturers Description The STD01N and STD01P are enhanced Darlington transistors with built-in drivers and temperature compensation diode. Manufactured using the unique Sanken thin-wafer production tech [ ... ]

STD01P PDF Datasheet Download