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Switching with transistors PNP and NPN (the basics)

Switching with transistors PNP and NPN (the basics)

Old video from my former channel Radioam232, approx 2008. How to use PNP and NPN transistors as a switch. Switch mode = saturating the base from the switch transistor or Darlington with enough voltage/current, so the issue is not difficult.Only problem: a too high base current immediately (!) damages the transistor (Ts 1 and/or TS 2) and there is no (...) indication from that damage. Only that ""it"" does not work.

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In thematical order you can find these video’s under the “comments” section. My books about electronics are available via the website from “Lulu”, search for author “Ko Tilman” there. My books are also available via Barnes and Noble and via Amazon. Regarding all my video’s: I constantly keep them actual, so the original video’s with the most recent information are always on YouTube. That is the source, and search there. When...


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  1. Date: August 27, 2017 at 21:28
    Author: MrTriac

    There is a flaw in your schematic. Let me explain… In that configuration the first transistor (T1_NPN) cannot assure the saturation condition in order to switch off completely the PNP transistor (Vbe<0.4V). Tying base to collector brings T1 (NPN) in active region (0.7V). Instead use a PNP tr. for T1. BTW, it's a good practice to assign a letter/number for every element in the schematic (T1, T2, R1…).

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