Protecting Your MOSFET Gates: Simple Techniques That Save Circuits
MOSFETs are powerful switching components, but their gates are delicate and easily damaged by voltage spikes or static discharge. Without proper gate protection, your circuit may fail unexpectedly or permanently damage the MOSFET.
⚠️ The Problem :
The gate of a MOSFET acts like a capacitor. If hit with a voltage beyond its rating (usually ±20V), it can puncture the gate oxide layer, ruining the device. Even accidental static discharge from your hand can do this.
🔧 The Solution :
Use a gate resistor and TVS (transient voltage suppression) diode to protect against spikes. A resistor (10Ω–100Ω) slows down the switching, absorbing inrush current. A TVS diode clamps any surge above the gate voltage limit.
🔍 Practical Example :
Say you’re driving a MOSFET gate with 10V and want to use a 100Ω gate resistor:
If the gate charge (Qg) is 30nC,
Switching time = Qg / Igate = (30nC) / (10V / 100Ω) = 300ns,
which slows down the rise time safely and avoids gate ringing.
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