Comparing diode combinations with NPN and PNP transistors (BJT)

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Why don’t two diodes connected anode to anode (or cathode to cathode) function as PNP or NPN transistors?

Simple diodes are PN junctions that prevent electron flow in one direction through the negative charge and (some) transistors are PNP or NPN with two PN junctions so why cannot I use two diodes connected cathode to cathode or anode to anode (so that two anodes or two cathodes present on both sides) to replace a transistor/do not work that way?

Edit: Just reread the rules and it says that the question must be clear from the title (but I can’t change it) so I’ve put it on the first line.

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3 Answers

Anonymous 0 Comments

There is more to a transistor, than just two PN junctions. The base must be thin – thinner than the mean charge travel distance, so the charges can randomly cross the base and get to the collector. The emitter is small, but heavily doped, so it contains more charge carriers. The collector is big, so it can catch more stray charges.

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