Question about common-collector amplifier page

Discussion in 'General Electronics Chat' started by jut, Mar 12, 2008.

  1. jut

    Thread Starter Senior Member

    Aug 25, 2007
    224
    2
    http://www.allaboutcircuits.com/vol_3/chpt_4/6.html

    "It is called the common-collector configuration because (ignoring the power supply battery) both the signal source and the load share the collector lead as a common connection point:"

    [​IMG]

    I'm confused, why is this called the common-collector if the collector on the transistor only connects to the positive side of the battery?
     
  2. thingmaker3

    Retired Moderator

    May 16, 2005
    5,072
    6
    "Common" in this context does not mean "ground." It means "shared" or "mutual."
     
  3. Shelton

    Member

    Mar 13, 2008
    19
    0
    The input is connected to the Base
    The output is connected to the Emitter

    Whats left over? the Collector - hence its a common collector.

    This works for all three configurations.

    Try it! :)
     
  4. cumesoftware

    Senior Member

    Apr 27, 2007
    1,330
    10
    In this case, the collector can be connected to Vcc or to ground. In the case of a NPN transistor, it will be connected to Vcc. In the case of a PNP transistor, it will be connected to ground.

    So, it is better to think that "common" means that it is not connected to the input or the output, although it does not always means that the "common" is connected directly to ground or Vcc.
     
  5. Colin Mac

    Member

    Mar 11, 2008
    18
    0
    The collector is common to both the input and output.
     
  6. jut

    Thread Starter Senior Member

    Aug 25, 2007
    224
    2
    Well OK. If you imagine the load power supply battery shorted out, then the signal source and the load share the Collector as a common point. I was imaging the power supply battery being open.

    Thanks for the help guys.
     
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