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Is the following a correct understanding of an NPN transistor?

enter image description here Basically, a positive voltage source needs to flow through the Base of an NPN transistor and out through the Emitter, so it needs to flow in (via the base) from a more positive source than it flows out (via the emitter).

Is this a correct understanding of what makes a transistor turns on? Is there anything else that might be added to it, such as how much current/voltage is required to turn the transistor 'on' or if there's a minimum voltage/transistor that needs to flow from the through the Base to the Collector for it to 'continue' to flow through.

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    \$\begingroup\$ Keep in mind that BJT transistors are current controlled devices. The statement "positive voltage source needs to flow" does not make sense. It is current that "flows", by applied force of voltage, so to speak. \$\endgroup\$
    – Maple
    Commented Jan 18, 2020 at 7:44
  • \$\begingroup\$ Maple...are you really sure? Can you proove it or is it just a believe? In fact, BJTs are voltage controlled!! Several explanations are proofs are available!! \$\endgroup\$
    – LvW
    Commented Jan 18, 2020 at 9:30
  • \$\begingroup\$ researchgate.net/publication/… \$\endgroup\$
    – LvW
    Commented Jan 18, 2020 at 9:44
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    \$\begingroup\$ @LvW Yes, from a semiconductor device physics point of view the transistor is controlled by voltage. But engineers usually use a higher level abstraction of the transistor, where it is useful to view the current as the controlling factor, since the collector current is proportional to the base current. I think you are being needlessly pedantic. \$\endgroup\$
    – Elliot Alderson
    Commented Jan 18, 2020 at 14:11
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    \$\begingroup\$ @LvW Wouldn't it be more correct to say that the transistor is controlled by semiconductor energy levels? Saying that it is controlled by voltage makes it hard to explain how phototransistors work. \$\endgroup\$
    – Elliot Alderson
    Commented Jan 18, 2020 at 15:46

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The image of Figure 1 may help a little.

enter image description here

Figure 1. Horowitz and Hill, The Art of Electronics. "Transistor Man" looks at the current at the base, and adjust the current at the collector so as to be a multiple of the base current.

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  • \$\begingroup\$ Perhaps it is useful (and necessary) to add that the shown figure is an illustration to a simplified explanation of the transistor principle. In a succeeding paragraph of the mentioned book (Art of Electronics) it is explained that the BJT is in fact a device where the collector current is determined and controlled by the base-emitter voltage only !! The base current is nothing else than an unwanted by-product which, however, cannot be avoided. \$\endgroup\$
    – LvW
    Commented Jan 18, 2020 at 11:59
  • \$\begingroup\$ I was waiting for you. :^) Despite my username, transistor theory is not my strong point. \$\endgroup\$
    – Transistor
    Commented Jan 18, 2020 at 12:16
  • \$\begingroup\$ I think your transistor theory is just fine. It is the appropriate model of a transistor for engineering purposes. Arguments about whether the transistor is voltage controlled or current controlled belong on physics.SE \$\endgroup\$
    – Elliot Alderson
    Commented Jan 18, 2020 at 14:12
  • \$\begingroup\$ @Elliot Alderson, I disagree: Each electronic engineer working with transistors must know how the BJT really works. This is the result of my experience!! Do you need some examples ? Look here: researchgate.net/publication/… \$\endgroup\$
    – LvW
    Commented Jan 18, 2020 at 15:18
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    \$\begingroup\$ @LvW In what way is my example a misconception? Oh, and I can explain how RE provides feedback because I do not ignore the relationship between Vbe and Ib...but I don't need to enforce a strict use of the word controlled. In fact, I don't have to use the word controlled at all. If you really understand how the BJT works you don't need to rely on such generalizations. Maybe you taught that way, but I don't. \$\endgroup\$
    – Elliot Alderson
    Commented Jan 18, 2020 at 16:05

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