Ac coupled Amplifier question

Discussion in 'Homework Help' started by Panterulez, Apr 8, 2009.

  1. Panterulez

    Thread Starter New Member

    Mar 25, 2009

    According to my notes, it is stated the CC amplifier, an emitter-follower gives low output resistance and buffers the high gain stage from the relatively load resistance. I just don't seem to understand what this exactly means ? Can anyone enlighten me
  2. The Electrician

    AAC Fanatic!

    Oct 9, 2007
    The load is 250 Ω. If it had been connected to the collector of the C-E amplifier (through C5), then the effective collector load resistance would have been 4700 Ω in parallel with 250 Ω, and the gain of the C-E stage would have been drastically reduced.

    The emitter follower has a low output resistance to drive the low resistance load, and a high input impedance to avoid loading the C-E stage.
  3. jasperthecat


    Mar 26, 2009
    You could look at the theory here

    or Wikipedia to better understand the various transistor configurations of

    Common Emitter, Common Base & Common collector.

    A little cheat sheet on BJT configurations helps

    CE Zin =medium Zout =medium Gain >>1

    CC Zin = Hi Zout = Lo Gain <1

    CB Zin = Lo Zout = Medium Gain >>1

    Hope this helps