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A MOSFET's gate behaves like a capacitor. The gate resistor limits the peak current from the driver and sets how fast the gate charges — which controls the switching speed, the switching loss, and the amount of ringing and EMI. A smaller resistor switches faster (less loss) but rings more; a larger one is slower and softer.
| Quantity | Formula |
|---|---|
| Peak gate current | IG(peak) = Vdrive / (RG(ext)+RG(int)) |
| Switching (Miller) time | tsw = Qgd × RG / (Vdrive−Vplateau) |
| Gate-drive power | Pgate = Qg × Vdrive × fsw |
The gate driver must supply the peak current, and its output stage (plus the resistor) dissipates the gate-drive power.
It limits the peak current from the gate driver and sets how fast the MOSFET gate charges and discharges, which controls switching speed, switching loss, ringing, and EMI.
Yes — a smaller resistor lets more current flow into the gate, so it switches faster with lower switching loss, but it also increases voltage overshoot and EMI.
Too little resistance causes severe ringing (from gate and layout inductance), overshoot that can exceed the gate rating, and radiated EMI. A few ohms of damping is almost always needed.
During switching the gate voltage briefly flattens while the gate-drain charge Qgd is delivered and the drain voltage transitions. Most switching loss happens here, so this "plateau" governs the switching time.
The total charge needed to fully turn the gate on, from the datasheet. With Qgd (the Miller portion) it lets you estimate switching time and gate-drive power.
It must supply at least the peak gate current, Vdrive/(RG(ext)+RG(int)). Large MOSFETs with small resistors can need 1–4 A drivers.
A few ohms built into the MOSFET package (RG(int)). It adds in series with your external resistor and cannot be reduced, so include it in the total.
Yes — a common technique uses a resistor for turn-on and a diode-bypassed lower resistance for faster turn-off (or vice versa) to independently tune the two edges.
A larger resistor slows the transition, increasing the voltage-current overlap and therefore the switching loss. See our MOSFET Power Loss Calculator to quantify it.
Separate gate resistors damp high-frequency oscillation between the devices and help them share current, preventing one from switching much faster than the others.
In the driver output stage and the gate resistors, split between turn-on and turn-off. It equals Qg×Vdrive×fsw and grows with frequency.
Follow the datasheet — typically 10–12 V for standard MOSFETs and 4.5–5 V for logic-level parts. Higher VGS lowers RDS(on) but must stay under the gate rating.
It is a good first-order figure for choosing RG. Real edges also depend on layout inductance, driver strength, and the load, so verify on the bench for critical designs.
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