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SESK: Stuff Everyone Should Know · sesk.info/hame-zener-constant-voltage

What is the most useful characteristic of a Zener diode?

A constant voltage drop even when the current changes.

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  1. A constant voltage drop with varying current ✔
  2. A constant current drop with varying voltage
  3. A negative resistance region

Why: In reverse breakdown a Zener holds its voltage nearly steady while the current swings. That makes it handy for voltage references and simple regulators.

Huh, didn't know that: A switchmode voltage regulator works by varying the duty cycle of pulses fed into a filter (E7D02).

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Why does an analog design engineer open the databook of Zener diodes? To find a reference.
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References

Answer: A constant voltage drop with varying current. In reverse breakdown a Zener holds its voltage nearly steady while the current swings. That makes it handy for voltage references and simple regulators.

  1. NCVEC 2024-2028 Amateur Extra Question Pool, E6B01 (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
    B. A constant voltage drop under conditions of varying current
    Checked 2026-10-11.
  2. NCVEC 2024-2028 Amateur Extra Question Pool, E7D02 (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
    B. By varying the duty cycle of pulses input to a filter
    Checked 2026-10-11.

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