Transistor: anode vs cathode

Discussion in 'General Electronics Chat' started by ak_47_boy, Feb 3, 2014.

  1. ak_47_boy

    Thread Starter New Member

    Jan 29, 2014
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    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...
     
  2. bountyhunter

    Well-Known Member

    Sep 7, 2009
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    diodes have anodes and cathodes, transistors have a base, emitter and collector.
     
  3. bountyhunter

    Well-Known Member

    Sep 7, 2009
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    They are certainly not symmetrical in structure. The E-B and B-C junctions are very different.
     
  4. MikeML

    AAC Fanatic!

    Oct 2, 2009
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    They haven't been symmetrical since the original Bell Lab transistor...
     
  5. crutschow

    Expert

    Mar 14, 2008
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    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.
     
  6. Dave_UYZ

    New Member

    Jan 16, 2014
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    It has a lot to do with the direction that the electrons are travelling
     
  7. ian field

    Distinguished Member

    Oct 27, 2012
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    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.
     
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