Two stage common emitter amplifier

Discussion in 'General Electronics Chat' started by jut, Dec 4, 2009.

  1. jut

    Thread Starter Senior Member

    Aug 25, 2007
    224
    2
    I am trying to achieve maximum gain from two CE stages. The input signal is 50mVp-p and the load is 5k.

    I attached the schematic and voltage into and output signals. The most I could muster was a gain of 207. Can someone tell me if it's possible to get more? Are there any flaws in this setup holding me back?
     
  2. Audioguru

    New Member

    Dec 20, 2007
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    896
    R16 and R18 provide some negative feedback to reduce distortion and reduce the maximum gain. Short them for max gain.

    The load is 1k, not 5k. The gain is higher if the load is 5k and then the collector resistor value of the second transistor can be increased for even more gain.
     
  3. KL7AJ

    AAC Fanatic!

    Nov 4, 2008
    2,040
    287

    Assuming your input and output impedances are about equal, that's about 46 db of gain. Theoretical maximum power gain for a BJT is about 23 dB. You're right on the money.


    eric
     
  4. Jony130

    AAC Fanatic!

    Feb 17, 2009
    3,957
    1,097
    Yes its passable to get more gain
    I get 1KV/V
     
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  5. S_lannan

    Active Member

    Jun 20, 2007
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    well if you can manage a gain of 50x per stage you could get up to 2500 total...
     
  6. jut

    Thread Starter Senior Member

    Aug 25, 2007
    224
    2
    wow, nice! I need to study that circuit. I haven't seen that kind of emitter configuration yet. thanks.
     
  7. lmartinez

    Active Member

    Mar 8, 2009
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    6
    Can you expand on this. Thank you in advance:)
     
  8. lmartinez

    Active Member

    Mar 8, 2009
    224
    6

    Mr. AudioGuru:

    Can you share some of your knowledge? How are R16 and R18 providing negative feedback to such circuit configuration to reduce distortion. Your feedback is highly appreciated. Thank you
     
  9. Audioguru

    New Member

    Dec 20, 2007
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    An unbypassed emitter resistor produces negative feedback. That is why the gain is reduced. The distortion is also reduced.
     
  10. ELECTRONERD

    Senior Member

    May 26, 2009
    1,146
    16
    Actually I've read that a maximum gain of 25dB is allowed per stage (Av=17.8≈18), and not 23dB (Av=14). I suppose I am being a bit picky, but I"m sure he'll want to squeeze out all the gain he can get.

    Another way for the op to increase gain is by adding a cap in parallel with the emitter resistor. This will increase Av by quite a stretch.

    Austin
     
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