MAXScanner engineering calculator
Updated 2026-09-18
MOSFET Gate Drive Calculator — Gate Current, Power & Switching Time
Estimate MOSFET gate-drive average current, drive power, peak current and a charge-based switching-time estimate from total gate charge, drive voltage, frequency and entered gate resistance.
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- 1.Convert: Qg = 50 nC = 0.00000005 C; f = 100 kHz = 100,000 Hz.
- 2.Average gate current: Qg × f = 0.00000005 × 100,000 = 5 mA.
- 3.Gate-drive power: Qg × Vdrive × f = 50 nC × 10 V × 100 kHz = 50 mW.
- 4.Peak gate current: Vdrive ÷ Rg = 10 ÷ 10 = 1 A; Charge-based switching estimate: Qg ÷ Ipeak ≈ 50 ns.
Formula, example and limits
Iavg=Qg·f; Pgate=Qg·Vdrive·f; Ipeak≈Vdrive/Rg; tswitch≈Qg/Ipeak.
50 nC at 100 kHz and 10 V needs about 5 mA average gate current and 50 mW ideal gate-drive power.
- Gate-charge timing is a first-order estimate; Qg varies with VGS, VDS and operating point.
- Driver output resistance, internal gate resistance, Miller plateau, parasitics, dead time and EMI constraints require datasheet-level design.
Frequently asked questions
Why can peak gate current be much higher than average current?
The gate draws charge in short switching pulses. Average current is Qg times switching frequency, while instantaneous current is set by driver and gate-path impedance.
Should I choose the smallest possible gate resistor?
Not automatically. Faster edges can reduce switching loss but increase ringing, EMI, overshoot and driver stress.
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