IGBTs and MOSFETs are the two most common power switches, but they have different characteristics. Choosing the right one is key to an efficient and reliable design.
1. Operating Principle
A MOSFET is a voltage-controlled device that behaves like a resistor when on. An IGBT combines the simple gate drive of a MOSFET with the high-current and low-saturation-voltage capability of a bipolar transistor.
2. Switching Speed
MOSFETs are the clear winners here. They can switch at frequencies of several hundred kHz, or even into the MHz range. IGBTs are generally limited to frequencies below 100 kHz due to their "tail current" during turn-off.
3. Voltage and Current Ratings
IGBTs typically handle higher voltages and currents. While high-voltage MOSFETs exist, IGBTs are generally more cost-effective for applications above 600V and tens of amps.
4. Conduction Loss
At low currents, MOSFETs have lower conduction losses due to their resistive nature (Rds(on)). At high currents, the fixed saturation voltage (Vce(sat)) of an IGBT results in lower conduction losses.
Conclusion: Which to Choose?
- Use a MOSFET for: High-frequency applications (like switching power supplies) and low-voltage applications (below 200V).
- Use an IGBT for: High-power, high-voltage, lower-frequency applications (like motor drives and solar inverters).