MOSFET switch and gate-drive losses
Gate-charge switching estimates and a self-consistent linear RDS(on) thermal model.
Development preview. Check the assumptions below before relying on a result. Calculations run in your browser.
How it calculates
Assumptions
- Exactly zero or unity duty represents a DC off/on state with no periodic switching events.
- Hard-switching constant-current overlap estimate. Gate charge must be specified at the actual operating drain voltage/current.
- Coss is energy-equivalent (2Eoss/V²), not a small-signal capacitance. Gate loss is in the driver supply and is excluded from MOSFET heat.
- Effective thermal resistance must represent the actual assembly. This model omits reverse recovery and dead-time loss.
Worked example
These are the calculator's default inputs. Change any input above to recalculate.
Inputs
- Switched voltage
- 24 V
- On-state current
- 5 A
- Conduction duty
- 0.5
- Switching frequency
- 100000 Hz
- RDS(on) at 25 °C
- 0.02 Ω
- Linear resistance temperature coefficient
- 0.004 1/K
- Total gate charge
- 4e-8 C
- Miller gate charge
- 1e-8 C
- Gate-drive voltage
- 10 V
- Gate plateau voltage
- 4 V
- Total turn-on gate resistance
- 10 Ω
- Total turn-off gate resistance
- 5 Ω
- Energy-equivalent output capacitance
- 2e-10 F
- Ambient temperature
- 25 °C
- Effective thermal resistance
- 40 K/W
- Maximum junction temperature
- 150 °C
Results
- MOSFET loss
- 0.448708 W
- Estimated junction temperature
- 42.9483 °C
- Voltage transition at turn-on
- 1.66667e-8 s
- Voltage transition at turn-off
- 1.25e-8 s
- Initial gate-current estimate
- 1 A
- Turn-on voltage slew
- 1440000000 V/s
- Hot conduction loss
- 0.267948 W
- Overlap and Coss loss
- 0.18076 W