Side-by-side comparison
| Parameter | Power MOSFET | IGBT |
|---|---|---|
| Device Structure | Unipolar — electrons only; MOSFET channel + body diode | Bipolar — minority carrier injection gives conductivity modulation |
| Conduction Loss Mechanism | I²·R_DS(on) — on-resistance increases with voltage rating | V_CE(sat) + I·r — quasi-flat vs current; lower at high current |
| R_DS(on) vs Voltage Rating | R_DS(on) ∝ V_BR^2.5 — doubles every 150 V rise (Si MOSFET) | V_CE(sat) weakly dependent on voltage rating — advantage above 300 V |
| Switching Speed | Very fast — 10 ns–100 ns; no minority carrier storage | Slower — 0.5–3 µs turn-off tail due to stored charge |
| Switching Frequency | 100 kHz – several MHz (Si); GaN up to 10 MHz | 1 kHz – 50 kHz typical |
| Optimal Voltage Range | < 300 V (Si); < 650 V (SiC/GaN) | 300 V – 6500 V |
| Gate Drive Voltage | +10 to +15 V (turn-on); 0 V turn-off (some need −5 V) | +15 V turn-on; −5 to −8 V turn-off to prevent spurious turn-on |
| Body Diode | Present — fast in Si, excellent in SiC; slow recovery in standard Si | No true body diode; anti-parallel diode added externally; co-pack diode is separate |
| Example Devices | IRF540 (100 V, 28 A), C2M0080120D SiC MOSFET (1200 V) | FGL60N100 (1000 V), Infineon FF300R17KE4 (1700 V, 300 A module) |
| Thermal Runaway Risk | R_DS(on) rises with temp — self-limiting; positive temp coeff | V_CE(sat) slightly negative temp coeff at low current — parallel units need current sharing care |
Key differences
At 100 V, a Si MOSFET (e.g. IRF540, R_DS(on) = 77 mΩ) has far lower conduction loss than an IGBT because conductivity modulation does not offset the stored charge switching loss at the same voltage. Cross over to 600 V and the Si MOSFET's R_DS(on) explodes due to the R_DS(on) ∝ V_BR^2.5 relationship, while the IGBT's V_CE(sat) stays near 2 V regardless. SiC MOSFETs (e.g. C2M0080120D, 1200 V, 80 mΩ) break this rule — SiC's wider bandgap gives R_DS(on) values competitive with IGBT even at 1200 V, combining MOSFET switching speed with IGBT voltage range, which is why SiC dominates new EV inverter designs (Tesla Model 3 inverter, 650 V SiC).
When to use Power MOSFET
Use a Si MOSFET for switching converters below 200 V where switching frequency above 100 kHz is needed. Example: a 12 V to 3.3 V synchronous buck converter for a server motherboard uses a Si MOSFET pair (IRFS7437, 40 V, 195 A) switching at 600 kHz with < 0.5% total losses.
When to use IGBT
Use an IGBT for motor drives, welders, and inverters in the 300 V–3300 V range where conduction loss at high current dominates and switching frequency below 50 kHz is acceptable. Example: a 37 kW three-phase motor drive uses a Semikron SKM200GB12T4 IGBT module (1200 V, 200 A) at 8 kHz with V_CE(sat) of 2.1 V.
Recommendation
Below 200 V: choose MOSFET — lower R_DS(on) and faster switching win every time. Above 400 V with motor drive currents: choose IGBT unless you can afford SiC. For new designs above 650 V where switching frequency matters, choose SiC MOSFET — it is the future default. Si MOSFET at high voltage is an engineering mistake, not a trade-off.
Exam tip: Examiners ask students to explain why MOSFET conduction loss increases with voltage rating while IGBT conduction loss does not — cite R_DS(on) ∝ V_BR^2.5 for MOSFET vs the bipolar conductivity modulation of IGBT that keeps V_CE(sat) nearly constant.
Interview tip: A placement interviewer at an EV or power conversion company will ask you why Tesla switched to SiC MOSFETs in the Model 3 inverter — answer: SiC MOSFET (650 V) provides R_DS(on) comparable to IGBT at the same voltage but with 10× faster switching, reducing inverter switching losses by ~75% and improving range per charge.