The STD9N40M2 from STMicroelectronics is a MOSFET with Continous Drain Current 6 A, Drain Source Resistance 590 to 800 Milliohm, Drain Source Breakdown Voltage 400 V, Gate Source Voltage - 25 to 25 V, Gate Source Threshold Voltage 2 to 4 V. Tags: Surface Mount. More details for STD9N40M2 can be seen below.