The Si4840BDY from Vishay is a MOSFET with Continous Drain Current 19 A, Drain Source Resistance 7 to 12 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 Si4840BDY can be seen below.