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enter image description here To know the values of \$I_{B},V_{CE}\$ and \$I_C\$ In the saturation region, all I have to do is look at the point A in the above figure, right? But that can't be the case since \$I_B\$ there is 1/100 times \$I_C\$, assuming β=100. However, the minimum \$I_B\$ needed for saturation, typically, is only \$\frac{1}{20}I_C\$ with a forced \$\beta\$ of 20. So, what am I missing here?

The figure in the question is adopted from this video https://youtu.be/QMI30-GxG5k?t=420

Jack
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  • I believe you've been made aware of the different definitions used for "saturation" in previous questions. Why persist using this one? – Tim Williams Dec 24 '23 at 18:52
  • Sorry Tim, but I don't get what you mean. – Jack Dec 24 '23 at 18:54
  • You're basically asking "why doesn't [definition 2] mean [definition 1]?" The figure defines saturation as the labeled region, period; the other definitions (B-C forward bias, forced hFE) are just that: other definitions. Does that make sense? – Tim Williams Dec 24 '23 at 19:07
  • What do the coordinates of the point A in the figure tell me? – Jack Dec 24 '23 at 19:09
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    Take a look here https://electronics.stackexchange.com/questions/311243/bjt-base-current-calculation/311306#311306 – G36 Dec 24 '23 at 19:25
  • Or here https://electronics.stackexchange.com/questions/276146/a-question-about-vce-of-an-npn-bjt-in-saturation-region/276266#276266 – G36 Dec 24 '23 at 19:27
  • @Jack This picture shows you clearly delineated modes. Do you notice that the $\beta$ can still be 100 while also in shallow saturation (CB junction voltage of NPN nearer to 0 V)? As the saturation deepens (more to the left) the $\beta$ takes a deep dive. But only as the CB junction nears to a diode drop magnitude. That's all there is to it. – periblepsis Dec 24 '23 at 19:29
  • With assumption of beta=20 you are forcing 5 times higher Ib. Another words, you forgot about inversion: lower Beta assumption -> higher Ib -> deeper saturation. – Michal Podmanický Dec 24 '23 at 20:16
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    @Jack I think you are like a character in the blind men and an elephant story. You read one description from a limited perspective, then another from a different perspective also limited in scope, and so on. You then find yourself here, today, wondering who's been lying to you. Just as in the fable. I think it is high time for you to face the actual creature itself: the Shockley diode equation. Let loose of old ideas, embrace this one, and then understand diodes and BJTs well. – periblepsis Dec 24 '23 at 23:56
  • @periblepsis thanks – Jack Dec 25 '23 at 02:52
  • You make assumptions AND wonder why an arbitrary graph does not agree with your assumptions. Calculate β from graph and your issue is moot. – StainlessSteelRat Dec 25 '23 at 06:39

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