The Si4490DY from Vishay is a MOSFET with Continous Drain Current 4 A, Drain Source Resistance 65 to 90 milliohm, Drain Source Breakdown Voltage 200 V, Gate Source Voltage -20 to 20 V, Gate Source Threshold Voltage 2 V. Tags: Surface Mount. More details for Si4490DY can be seen below.