The Si4124DY from Vishay is a MOSFET with Continous Drain Current 20.5 A, Drain Source Resistance 6 to 9 milliohm, Drain Source Breakdown Voltage 40 V, Gate Source Voltage -20 to 20 V, Gate Source Threshold Voltage 1 to 3 V. Tags: Surface Mount. More details for Si4124DY can be seen below.