The TK4A50D from Toshiba is a MOSFET with Continous Drain Current 4 A, Drain Source Resistance 1700 to 2000 Milliohm, Drain Source Breakdown Voltage 500 V, Gate Source Voltage -30 to 30 V, Gate Source Threshold Voltage 2.4 to 4.4 V. Tags: Through Hole. More details for TK4A50D can be seen below.