Folded cascode op amp

Discussion in 'General Electronics Chat' started by qwerty11, Dec 11, 2015.

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  1. qwerty11

    Thread Starter New Member

    Apr 9, 2013
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    My op amp is producing very low gain. Please can anyone see where my mistake is? I've done a DC analysis but I can't see the mistake. Thank you.
    upload_2015-12-11_20-41-9.png
    The bode plot between input and output signals is -6.1kdB and 45 degrees constant:
     
  2. dl324

    Distinguished Member

    Mar 30, 2015
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    Can't make heads nor tails out of that schematic. Too much clutter, poor choice of colors on a black background.
     
  3. kyka

    New Member

    Jun 7, 2015
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    There is not enough voltage at the gates of M2 and M3. As a consequence, after the voltage drop M4 and M5 saturate and can't pull enough current to forward bias M8 and M9 and they saturate as well.
     
  4. qwerty11

    Thread Starter New Member

    Apr 9, 2013
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    Sorry for the late reply, I thought I would get an email notification for this.
    I was wondering what books or online resources you used to be able to understand what to do? I'm really struggling and I don't know what initial steps I should take to go about creating a circuit design like this. Like which transistors should be in saturation, how I can decide on the bias voltages and currents, other than just running a sweep and choosing the best values - I am not using logic, just repetition to solve right now.
    Thank you.
     
  5. bertus

    Administrator

    Apr 5, 2008
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