The STD7NK40ZT4 from STMicroelectronics is a MOSFET with Continous Drain Current 5.4 A, Drain Source Resistance 850 to 100 Milliohm, Drain Source Breakdown Voltage 400 V, Gate Source Voltage -30 to 30 V, Gate Source Threshold Voltage 3 to 4.5 V. Tags: Surface Mount. More details for STD7NK40ZT4 can be seen below.