IRF3205PBF

The IRF3205PBF from Infineon Technologies (formerly International Rectifier) is a 55V N-channel power MOSFET with 8mΩ on-resistance and 110A continuous drain current, making it one of the most capable devices in the sub-60V class. The ultra-low RDS(on) of 8mΩ means that at 20A load, the voltage drop across the MOSFET is only 160mV and conduction loss is just 3.2W — significantly less than the IRF540N (44mΩ) which would dissipate 17.6W at the same current. This makes the IRF3205 the preferred choice for high-efficiency applications where thermal management is critical. The 55V rating is suitable for 12V and 24V systems (including automotive 14.4V), where load dump transients can reach 40V but not 55V. The 146nC total gate charge is relatively high, making the IRF3205 better suited for switching frequencies below 100kHz; at higher frequencies, the gate drive losses become significant. The PBF suffix denotes the lead-free (Pb-free) version in TO-220 package.

The IRF3205PBF operates as an N-channel enhancement-mode MOSFET. When VGS exceeds the threshold (2-4V), a conductive channel forms between drain and source. For minimum RDS(on) of 8mΩ, VGS must be at least 10V. At VGS=4.5V, RDS(on) is significantly higher (~15-20mΩ). The extremely low 8mΩ is achieved through a large silicon die with many parallel HEXFET cells, which also explains the high 3247pF input capacitance and 146nC gate charge. The gate driver must supply this charge rapidly for fast switching; a driver capable of 2A can switch the IRF3205 in approximately 75ns. However, the high Ciss means that at high frequencies (>100kHz), the gate drive power dissipation (Pgate = Qg × VGS × f) becomes substantial. At 50kHz, Pgate = 146nC × 10V × 50kHz = 73mW, which is manageable. At 500kHz, Pgate = 730mW, which may be problematic. The body diode has a forward voltage of 1.3V and reverse recovery time of 69ns, making it suitable for moderate-frequency freewheeling applications. For synchronous rectification at high frequencies, a MOSFET with faster body diode (or an external Schottky) is preferred.

IRF3205PBF pin assignment (TO-220-3, front view, pins down): Pin 1 (left) = Gate, Pin 2 (center) = Drain/Tab, Pin 3 (right) = Source. The metal tab on the back is electrically connected to Drain (Pin 2). For low-side switching, Source connects to GND and Drain to the load. Gate drive voltage of 10V provides minimum 8mΩ RDS(on). For logic-level drive, consider IRLZ44N which reaches full enhancement at 5V VGS.

• 12V Buck Converter: IRF3205 as high-side switch; 50kHz; VGS=10V; Schottky or sync rect on low side; 12V to 3.3V at 30A; Pcond = I²×RDS(on) = 900×0.008 = 7.2W
• Motor H-Bridge: 4× IRF3205; 24V DC motor at 30A; RDS(on) per device = 8mΩ; total bridge drop = 2×30A×8mΩ = 0.48V; very low loss
• Automative Load Switch: Battery → IRF3205 → load; VGS=10V from gate driver; 40A continuous; heatsink required
• Battery Protection: IRF3205 in series with battery; back-to-back for bidirectional cutoff; RDS(on)=8mΩ minimizes voltage drop
• Inverter: Full-bridge with 4× IRF3205; 12V to AC; 50Hz; low switching losses at this frequency

IRF3205PBF is a 55V/110A N-channel MOSFET from Infineon in TO-220 with 8mΩ RDS(on). The IRF3205SPBF is the D2PAK surface-mount version. The IRLZ44N provides logic-level 55V/47A with 22mΩ for 5V gate drive. The IRF1405 offers 55V/169A with 5.3mΩ for extreme current applications. The FDP8860 from onsemi provides 60V/80A with 7.5mΩ in TO-220. For lower voltage, IRF3808 provides 75V/140A with 2.2mΩ. The IPT004N03L from Infineon offers 30V/120A with 0.4mΩ for synchronous buck converters.