Can the diode ideality factor be lesser than 1 or very close to 1?

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  • ID and VD are the diode current and voltage, respectively
  • q is the charge on the electron
  • n is the ideality factor
  • k is Boltzmann’s constant
  • T is temperature in Kelvin
  • \$\begingroup\$ Where did the equation come from? What are D, S, q, VD, n, k and T? \$\endgroup\$
    – Transistor
    Commented Aug 6, 2018 at 13:41
  • 1
    \$\begingroup\$ @Transistor Looks like the Shockley Diode Equation... or was that something you wanted the OG to figure out? Lol woops \$\endgroup\$
    – user103380
    Commented Aug 6, 2018 at 14:18

1 Answer 1


The ideality factor adjusts the original Shockley diode equation to fit non-Germanium diodes more closely. There's also a series resistance term.

Equation 3.13 from the original 1950 paper from Bell System Technical Journal:

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The factor was added a few years later in a fascinating paper on radioactive p-n junction power sources.

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With silicon diodes the ideality factor is closer to 2 than 1. It can be higher than 2. A diode-connected silicon transistor operated at reasonable currents has an ideality factor close to 1.

I don't think it is ever less than 1 for a real diode, but that may not be correct.


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