The STD4NK80Z from STMicroelectronics is a MOSFET with Continous Drain Current 3 A, Drain Source Resistance 3000 to 3500 Milliohm, Drain Source Breakdown Voltage 800 V, Gate Source Voltage -30 to 30 V, Gate Source Threshold Voltage 3 to 4.5 V. Tags: Surface Mount. More details for STD4NK80Z can be seen below.