i need help with multistage amplifier plz

Discussion in 'The Projects Forum' started by CoMPiLeR, May 28, 2007.

  1. CoMPiLeR

    Thread Starter New Member

    May 28, 2007
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    hello

    can any one help me with suggesting a good configuration (cascode,cascade,common emitter,differential etc...) to get a voltage Gain of 1000 v/v?

    i tried 4 stages but it didnt workout for me!

    best regards,
     
  2. hgmjr

    Moderator

    Jan 28, 2005
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  3. CoMPiLeR

    Thread Starter New Member

    May 28, 2007
    3
    0
    my current configuration is (Differential - Cascade - Common Emitter (emitter Resistance) - Common Emitter (Emitter Resistance)) i got Av=4 k v/v and input and output impendace as desired but am having triuble with Flow and Fhigh :S
     
  4. CoMPiLeR

    Thread Starter New Member

    May 28, 2007
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    0
    thanx for the link..i hecked it out but i need to build it not using op-amps but BJTs...
    i only have problem with Flow now..i need it less than 200Hz...when i add couplin capcitor to the input signal i loose my gain :S!
     
  5. beenthere

    Retired Moderator

    Apr 20, 2004
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    Size matters - your coupling cap is probably too small a value.
     
  6. Ron H

    AAC Fanatic!

    Apr 14, 2005
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    Changing Flow is simply a matter of changing capacitor values. Achieving high bandwidth (Fhigh) and high gain is much more challenging. You can get more bandwidth by:
    1. Using more lower gain cascaded stages.
    2. Increasing power dissipation. This works because unwanted capacitance (Ccb, etc.) is relatively constant as a function of collector current, but resistor values go down, improving the high-frequency response.
    3. Using cascode stages to minimize the Miller effect.
     
  7. hgmjr

    Moderator

    Jan 28, 2005
    9,030
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    Can you post a schematic of the amplifier configuration that you have at the moment?

    Maybe we can then verify our suspicions as to the cause of your Flow problem.

    hgmjr
     
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