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SESK: Stuff Everyone Should Know · sesk.info/hame-mosfet-gate-zener

Why are Zener diodes sometimes connected between a MOSFET gate and its source or drain?

Protect the gate from static damage.

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  1. To protect the substrate from excessive voltages
  2. To provide a reverse-bias voltage reference
  3. To protect the gate from static damage ✔

Why: A MOSFET gate is separated by a very thin insulating layer. A small static charge can punch through it. A Zener clamps the voltage before that happens.

Huh, didn't know that: Point-contact diodes are commonly used as RF detectors (E6B09).

The dad joke
What did Johnny's mother do when she caught him zapping other kids with static electricity? She grounded him.
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References

Answer: To protect the gate from static damage. A MOSFET gate is separated by a very thin insulating layer. A small static charge can punch through it. A Zener clamps the voltage before that happens.

  1. NCVEC 2024-2028 Amateur Extra Question Pool, E6A12 (4th errata, Feb. 4, 2026) www.ncvec.org/downloads/2024-2028%20Extra%20Class%20Question%20Pool%20and%20Syllabus%20Public%20Release%20with%204th%20Errata%20Feb%204%202026.pdf
    D. To protect the gate from static damage
    Checked 2026-10-11.
  2. NCVEC 2024-2028 Amateur Extra Question Pool, E6B09 (4th errata, Feb. 4, 2026) www.ncvec.org/downloads/2024-2028%20Extra%20Class%20Question%20Pool%20and%20Syllabus%20Public%20Release%20with%204th%20Errata%20Feb%204%202026.pdf
    C. As an RF detector
    Checked 2026-10-11.

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