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The question pretty much sums up everything.

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No, you cannot swap emitter with a collector mainly due to the different doping (and size) between the collector and the emitter. The reverse beta \$\beta_R\$ will be much lower than the "normal" forward beta \$\beta_F\$. Also, \$V_{EB}\$ breakdown voltage is much lower than \$V_{CB}\$
For example my BC548B show this resoult: \$\beta_F = 250\$ at \$1\textrm{mA}\$ and \$\beta_R = 8.3\$ in reverse active mode for the same current. And breakdown voltage \$V_{EB} \approx 8.3V\$.

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A BJT is not symmetric. The emitter is much more heavily doped than the collector. Although a transistor can be operated in what is called the "reverse active" region, where the roles of emitter and collector are swapped, this is usually avoided because the current gain (beta) in such a configuration is much much lower. For the usual uses of a transistor, this is "bad".

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Bipolar transistors will function with emitter and collector swapped, however the performance will generally be much poorer in reverse mode. For example the ‘collector’ (what the manufacturer designates as emitter) breakdown voltage may be less than 10V (5V or less is typically guaranteed) and the hFE maybe 10 rather than 80V and 250 for an ordinary jellybean transistor.

Transistors have been made in the past that are symmetrical so the gain is reasonable in both configurations and the E-B breakdown is large in both configurations, however the applications these were aimed at (analog switches) are better served with MOSFETs and ICs made using MOSFETs. Muting transistors may still be available, which feature similar characteristics.

Saturation voltage in reverse mode can be lower than in forward mode, but again MOSFETs can do better again in most cases.


JFETs are typically symmetrical and you can swap source and drain, for example from the J111 datasheet:

enter image description here

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    \$\begingroup\$ Note however that power JFETs (like the SiC ones available from UnitedSiC/Qorvo) are typically not symmetric. \$\endgroup\$
    – Hearth
    May 3, 2022 at 14:07