I was wondering. What makes a transistor anode vs a cathode? Since they are symmetrical NPN or PNP shouldn't the anode and cathode be interchangeable on any device? Or collector/emitter i should say...

 

diodes have anodes and cathodes, transistors have a base, emitter and collector.

 

Since they are symmetrical NPN or PNP shouldn't the anode and cathode be interchangeable on any device?

They are certainly not symmetrical in structure. The E-B and B-C junctions are very different.

 

They haven't been symmetrical since the original Bell Lab transistor...

 

You can operate a transistor with the collector and emitter interchanged but the beta is typically very low in that configuration due to the asymmetrical structure of the collector and emitter. Also the base-emitter usually has a low breakdown voltage of perhaps 5V or so, thus using the emitter as the collector would limit the maximum allowed collector voltage to less than that value.

 

I was wondering. What makes a transistor anode vs a cathode? Since they are symmetrical NPN or PNP shouldn't the anode and cathode be interchangeable on any device? Or collector/emitter i should say...

It has a lot to do with the direction that the electrons are travelling

 

They are certainly not symmetrical in structure. The E-B and B-C junctions are very different.

Apparently some of the ancient germanium RF transistors, like the OC44 were more or less symmetrical.

There are probably a few modern examples, but you invariably get less gain if you swap C/E.