This post explains for the semiconductor K4145.
The Part Number is K4145, 2SK4145.
The function of this semiconductor is N-Channel 60V, MOSFET.
Manufacturers : NEC
Preview images :
The 2SK4145 is N-channel MOS Field Effect Transistor designed for high current switching applications.
• Low on-state resistance
RDS(on) = 10 mΩ MAX. (VGS = 10 V, ID = 42 A)
• Low input capacitance
Ciss = 5300 pF TYP.