The AUIRF4104S is an N-channel power MOSFET from Infineon's HEXFET® series, rated for 40 V drain-source breakdown and 75 A continuous drain current. The 5.5 mOhm maximum on-resistance at Vgs = 10 V and Id = 75 A defines the conduction loss floor — at full load, expect roughly 31 W of dissipation from Rds(on) alone before accounting for switching losses. Gate charge totals 100 nC at Vgs = 10 V. For a 100 kHz switching frequency, the gate driver must supply 10 mA average current to charge and discharge the gate capacitance; a driver with insufficient peak current will stretch the switching edges and increase crossover loss. The 140 W maximum power dissipation assumes an ideal heatsink; in a D2PAK on a standard FR4 board with 1 oz copper, the actual continuous dissipation will be lower — thermal resistance to ambient is dominated by the PCB copper area under the drain tab.
Gate drive and Vgs limits
The ±20 V maximum gate-source voltage is a hard limit — exceeding it risks oxide rupture. The 4 V threshold at 250 µA means the device is fully enhanced with a 10 V gate drive, but a 5 V logic-level drive may not saturate it to the rated Rds(on); check the transfer curve in the datasheet for the actual Rds(on) at Vgs = 5 V.