Question
What is the purpose of connecting Zener diodes between a MOSFET gate and its source or drain?
Answer Options
- A) To provide a voltage reference for the correct amount of reverse-bias gate voltage
- B) To protect the substrate from excessive voltages
- C) To keep the gate voltage within specifications and prevent the device from overheating
- D) To protect the gate from static damage
Correct Answer: D
Explanation
MOSFETs (Metal-Oxide-Semiconductor Field-Effect Transistors) use a very thin layer of silicon dioxide (a dielectric) to insulate the gate electrode from the conductive channel. While this insulation provides the advantage of extremely high input impedance, the thin oxide layer is extremely fragile and easily damaged by excessive voltage.
Even a small discharge of static electricity (ESD) during handling or operation can puncture the gate oxide, permanently destroying the transistor. Therefore, Zener diodes are often integrated internally or added externally between the gate and source/drain terminals to protect the gate from static damage. The Zener diode clamps any voltage spike that exceeds its breakdown voltage, shunting the excess current away from the sensitive gate insulation.
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