Choose the wrong power switch and the product pays for it forever: in heat, in efficiency, in failure rate. MOSFETs and IGBTs overlap in application space, but their loss physics and ruggedness profiles are different animals — and the choice is more systematic than most selection guides admit. Here is the real comparison.
The Loss Mechanisms Are Fundamentally Different
A MOSFET conducts through a resistive channel: conduction loss is I² × RDS(on) — proportional to the square of current. An IGBT conducts through a junction with a saturation voltage: conduction loss is roughly I × VCE(sat) — proportional to current. The consequences:
- At low currents and voltages, MOSFET resistance is cheap and IGBT fixed drops are wasteful.
- At high currents, the IGBT's linear loss grows more gently than the MOSFET's squared loss — one reason IGBTs dominate above ~600–1,200 V and hundreds of amps.
- Temperature behavior differs: MOSFET RDS(on) rises with temperature (positive TC — good for current sharing, bad for efficiency); IGBT VCE(sat) falls slightly then rises. Model at your operating temperature, not 25 °C.
Switching: Speed vs the Tail Current
- MOSFETs switch fast — tens of nanoseconds, limited mainly by gate drive strength and Qrr of body diodes. Efficient at 50–500 kHz and beyond (SiC variants push past 1 MHz).
- IGBTs carry a tail current: stored charge in the drift region keeps current flowing after the gate turns off, making every cycle pay a fixed turn-off energy (Eoff). Practical ceilings sit around 20–50 kHz for standard IGBTs — hard-brick territory for a 100 kHz design.
- Switching loss scales with frequency for both, but the IGBT's per-cycle cost is larger; the higher your switching frequency, the harder the decision tilts toward MOSFET (or wide-bandgap) devices.
The Voltage/Frequency Grid
| Application Zone | Typical Choice | Why |
|---|---|---|
| < 200 V, high frequency (DC-DC, point of load, BLDC drives) | Silicon MOSFET / GaN | Low RDS(on), fast switching, low gate charge |
| 200–600 V, moderate frequency (solar, OBC, servo drives) | SiC MOSFET vs superjunction Si MOSFET | SiC wins switching loss; Si wins unit cost |
| 600–1,200 V, low frequency (motor drives, welding, induction) | IGBT (or SiC at the premium end) | Conduction at high current, ruggedness, cost |
| 1,200–6,500 V (traction, grid) | IGBT (SiC entering) | High-voltage capability, mature modules |
Ruggedness: Where the IGBT Still Earns Respect
- Short-circuit withstand: IGBTs are specified to survive 10 µs of dead-short with desat detection reacting — a robust, well-understood protection scheme. MOSFETs fail faster and rely on quicker detection or cycle-by-cycle current limiting.
- Avalanche and dv/dt ruggedness differ by technology generation — compare single-pulse avalanche energy (EAS) and body-diode recovery (Qrr) for hard-switched bridges.
- Gate drive: both need isolated drivers above ~600 V bus, but IGBT desat protection, soft turn-off, and Miller clamp functions are mature catalog features. Design the protection as part of the device choice.
Where Wide-Bandgap Fits In
SiC MOSFETs now cover much of the classic IGBT space with lower switching loss and comparable voltage classes — the decision there is total system cost (SiC costs more per die but saves on magnetics, cooling, and efficiency). GaN stays dominant below ~650 V at high frequency. For a full treatment of the wide-bandgap trade, see our earlier guide — this article stays with the silicon-logic choice: which losses dominate your application, and at what frequency.
Selection Workflow
- Write down bus voltage, current (peak and continuous), switching frequency, and thermal budget.
- Estimate conduction and switching loss for the candidate device class at your real operating point — not the datasheet's.
- Check ruggedness requirements: short-circuit exposure, avalanche events, diode conduction duty.
- Confirm the gate-drive and protection ecosystem (desat, Miller clamp, isolation) matches the choice.
- Price the system, not the switch: heatsink, magnetics, and efficiency savings belong in the comparison.
JTDZ Tech stocks silicon MOSFETs, superjunction devices, IGBTs, SiC and GaN switches from Infineon, onsemi, ST, ROHM, and more — with loss curves to support the comparison. Send us your bus voltage, current, and frequency and we will quote the switch that wins at your operating point.
