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In the datasheet they express the hFE for a fixed Vce, sometimes they put 1 V, other times 10 V. But if the gain is independent of Vce this data is not really important, the hFE indicated in the datasheet is valid for any Vce?

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    \$\begingroup\$ Look up the "Early Effect." Also, don't design for a specific \$h_\text{FE}\$. \$\endgroup\$
    – jonk
    Commented Feb 24, 2021 at 21:29

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It varies with, Vce, Ic, temperature...

enter image description here

And even between two components from the same production line:

enter image description here

Image credits: 2N4401 datasheet

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  • \$\begingroup\$ The variation between 1 and 10 volts seems small .., thanks \$\endgroup\$
    – Mario
    Commented Feb 24, 2021 at 21:50
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    \$\begingroup\$ @Mario Sure, you could call that "pretty small" but that's for a "typical" transistor meaning, if you buy 1000 of this model transistor and measure them all, this is the average you get. Now look in the datasheet between what values \$h_{FE}\$ can vary. Note how the "Small signal current gain" varies between 40 and 500! Is that also a small variation? My point: in a circuit design don't rely on \$h_{FE}\$ having a predictable value. \$h_{FE}\$ is VERY unpredictable. Luckily in most circuits this is not an issue if you design for the lowest possible value of \$h_{FE}\$. \$\endgroup\$ Commented Feb 24, 2021 at 21:59
  • \$\begingroup\$ I can't find a 2N4401 datasheet with such graphics. I have tried NXP, Fairchild and Vishay. What is the manufacturer of the shown datasheet ? Thanks. \$\endgroup\$
    – andre314
    Commented Feb 24, 2021 at 22:11
  • \$\begingroup\$ onsemi.com/pub/Collateral/2N4401-D.PDF Sorry, forgot to put it in the answer \$\endgroup\$
    – devnull
    Commented Feb 24, 2021 at 22:11

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