When building or testing electronic circuits, one of the most common challenges you may face is protecting your sensitive components from Electrostatic Discharge (ESD). MOSFETs (Metal-Oxide-Semiconductor Field-Effect Transistors) are especially vulnerable to ESD, which can permanently damage them if not properly shielded. In simple terms, ESD is a sudden flow of electricity between two objects with different electrical potentials. This can happen when you accidentally touch a component or when there’s a voltage difference between objects.

The Problem :

Without proper protection, the gate of a MOSFET is prone to damage from even small ESD events. To fix this, you can use a Transient Voltage Suppression (TVS) diode to absorb the high-voltage spikes. Placing the TVS diode between the MOSFET gate and ground helps prevent ESD from reaching and damaging the MOSFET.

Practical Example :

Imagine you’re working on a DIY project and you’re building a simple LED circuit using a MOSFET. As you’re testing it, a small static shock (like rubbing your feet on a carpet) could potentially fry your MOSFET. To avoid this, you add a TVS diode at the gate, and even if you discharge static, the diode will safely redirect the surge to the ground.

Sample Calculation :

Let’s calculate the protection for a 10V surge with a TVS diode with a clamping voltage of 12V:

• Power dissipation (P) = Voltage (V) x Current (I)
• Assume the current during surge is 0.5A, so: $$P=12V\times 0.5A=6W$$

This means the TVS diode needs to handle 6W of energy during the surge.

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