This post explains for the semiconductor C4381.
The Full Part Number is 2SC4381. The package is FM20(TO220F) type.
The function of this semiconductor is Silicon NPN Triple Diffused Planar Transistor.
The manufacturers of this product is Sanken electric.
See the preview image and the PDF file for more information.
Preview images :
Silicon NPN Triple Diffused Planar Transistor (Complement to type 2SA1667/1668)
Application : TV Vertical Output, Audio Output Driver and General Purpose
Absolute maximum ratings
1. Vcbo = 150 V
2. Vceo = 150 V
3. Vebo = 6 V
4. Ic = 2 A
5. Ib = 1A