MOSFETs are essential in modern electronics, but their sensitive gate terminals can easily be damaged by voltage spikes. This is where MOSFET gate protection diodes come in—they act like voltage bodyguards, clamping unwanted spikes and preventing breakdown.

🔧 The Problem: Gate Overvoltage Damage

The gate of a MOSFET is essentially an insulated capacitor. Exceeding its voltage rating (often ±20V) even briefly can destroy it. Spikes can come from ESD, inductive kickbacks, or even long wire runs. Once the gate is damaged, your entire circuit could fail.

✅ The Solution: Clamp with Zener or TVS Diodes

To protect the gate, use a Zener diode (e.g., 15V) or a TVS (Transient Voltage Suppression) diode from gate to source. These components limit the gate voltage to a safe level, automatically kicking in when needed.

📦 Real-Life Example

Suppose you’re designing a fan controller using an IRF540N MOSFET. You drive the gate with 12V from a microcontroller circuit. Adding a 15V Zener diode from gate to source ensures that if a spike occurs, the gate voltage stays below 15V, saving the MOSFET.

🧮 Simple Calculation

Choose a Zener voltage slightly above your gate drive level. For 12V drive:

• Zener voltage ≈ 15V

• Power rating = (Expected leakage current) × (Zener voltage)
  If leakage is 5mA: P = 0.005A × 15V = 0.075W → Use a 0.25W Zener.

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