Q point changes

Discussion in 'The Projects Forum' started by M.wajahat, Jan 6, 2015.

  1. M.wajahat

    Thread Starter New Member

    Dec 9, 2014
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    In audio amplifier gain stage when i connect the stages in cascade manner by using a capacitor of 1000uF the qpoint of the stage changes. What's the solution??
     
  2. ronv

    AAC Fanatic!

    Nov 12, 2008
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    A schematic might help.
     
  3. M.wajahat

    Thread Starter New Member

    Dec 9, 2014
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    0
    Working well in proteus but not on breadboard
     
  4. #12

    Expert

    Nov 30, 2010
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    There are (3) 1000 uf capacitors in that drawing. Pick one.
     
  5. ronv

    AAC Fanatic!

    Nov 12, 2008
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    The capacitors are much bigger than you need, which means you probably used electrolytics. They have leakage current. So for example C2 will move the operating point. The simulation program does not use leakage current so it won't show. Change C2 to a 1 Ufd. film capacitor and see what happens.
     
  6. crutschow

    Expert

    Mar 14, 2008
    13,033
    3,241
    An electrolytic capacitor is polarized and the plus terminal must always be more positive than the negative terminal, otherwise they will conduct.
    Have you assured that is true for all the capacitors based upon the relative bias voltages?
     
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