MOSFET or IGBT? Choosing the Right Switch for Your Application

The choice between a MOSFET and an IGBT is decided by three numbers: blocking voltage, switching frequency and load current.

Below 400 V and above 20 kHz, use a MOSFET. Modern super-junction and SiC devices have low on-resistance and fast switching, which keeps switching losses small. This is the normal choice for DC-DC converters, motor drives at low voltage and battery systems.

Above 600 V and below 20 kHz, an IGBT usually wins. The conductivity modulation of an IGBT keeps conduction losses low at high current, which matters in welding machines, traction inverters and grid-tied equipment where switching frequency is modest.

SiC MOSFETs blur the line. They block 1200 V and switch fast, so they replace IGBTs in high-frequency, high-voltage designs. The trade-off is cost and the need for careful gate drive and layout.

Gate drive is not optional. A MOSFET needs a gate resistor sized for ringing, not just speed. An IGBT needs dead time control and often a negative gate bias to avoid parasitic turn-on.

Thermal design decides the rest. Calculate junction temperature at the worst-case ambient, not the nominal one. A part that runs at 140 °C in summer will fail in year two, whatever the datasheet says.