The Si4434DY from Vishay is a MOSFET with Continous Drain Current 3 A, Drain Source Resistance 129 to 162 milliohm, Drain Source Breakdown Voltage 250 V, Gate Source Voltage -20 to 20 V, Gate Source Threshold Voltage 2 to 4 V. Tags: Surface Mount. More details for Si4434DY can be seen below.