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SESK: Stuff Everyone Should Know · sesk.info/hamg-g6a05

About how much forward voltage does a silicon junction diode need before it conducts?

About 0.7 volts forward threshold.

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  1. 0.1 volt
  2. 0.7 volts ✔
  3. 1.0 volts

Why: A silicon diode starts conducting at about 0.7 volts forward bias. Below that, very little current flows. A germanium diode starts lower, near 0.3 volts.

Huh, didn't know that: An LED emits light when it is forward biased.

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References

Answer: 0.7 volts. A silicon diode starts conducting at about 0.7 volts forward bias. Below that, very little current flows. A germanium diode starts lower, near 0.3 volts.

  1. NCVEC 2023-2027 General Class Pool and Syllabus (6th Errata, Feb 4 2026) ncvec.org/downloads/General%20Class%20Pool%20and%20Syllabus%202023-2027%20Public%20Release%20with%206th%20Errata%20Feb%204%202026.pdf
    0.7 volts
    Checked 2026-10-11.

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