cause of doublet generation in opamp

Discussion in 'General Electronics Chat' started by manissri, Jan 24, 2006.

  1. manissri

    Thread Starter Member

    Jan 23, 2006
    10
    0
    hi all
    i am desing the folded cascode fully differential opamp with gian boost.
    i need the settling time should be 24 ns. for this i need around 250mhz ugb.
    one thing not clear to me that how the doublet are generated in my opamp which can degarde the settling time .
    means which pole and zero causing the slow settling.
    my mail opamp is folded cascode fully differential ( single stage)
    and the boosting opamp is also folded cascode single ended ( single ended)
    2.my second query is how to remove this doublets.
    regrds
    manish
     
  2. CoulombMagician

    Active Member

    Jan 10, 2006
    37
    0
    Please post a circuit.
     
  3. manissri

    Thread Starter Member

    Jan 23, 2006
    10
    0
    Hi coulumbmagician
    i am sending u my opamp ckt ..
    plz let me know the orining of doublet which degared me setting time.
    the ckt is attached
    manish
     
  4. manissri

    Thread Starter Member

    Jan 23, 2006
    10
    0
    Hi coulumbmagician
    i am sending u my opamp ckt ..
    plz let me know the orining of doublet which degared me setting time.
    the ckt is attached
    manish
     
  5. manissri

    Thread Starter Member

    Jan 23, 2006
    10
    0
    Hi coulumbmagician
    i am sending u my opamp ckt ..
    plz let me know the orining of doublet which degared me setting time.
    the ckt is attached
    manish
     
  6. CoulombMagician

    Active Member

    Jan 10, 2006
    37
    0
    I couldn't zoom in on the schematic but I see capacitors inside two different local feedback loops. I assume your problem is two different natural frequencies affecting the settling? Those loops are a good place to start looking.

    P.S. You don't need to have the detailed bias circuit as part of your simulation, the sim will run faster if you just use voltage and current sources. It also simplifies the circuit and makes it easier to troubleshoot.
     
  7. manissri

    Thread Starter Member

    Jan 23, 2006
    10
    0
    hi coulombmagician..
    plz click on the schematic and it will open in explorer r other web .
    so plz click on the schematic then it will automatically opened and u can view it very easly and can give a good suggestion ..
    regrds
    manish
    [




    quote=CoulombMagician,Jan 28 2006, 01:08 AM]
    I couldn't zoom in on the schematic but I see capacitors inside two different local feedback loops. I assume your problem is two different natural frequencies affecting the settling? Those loops are a good place to start looking.

    P.S. You don't need to have the detailed bias circuit as part of your simulation, the sim will run faster if you just use voltage and current sources. It also simplifies the circuit and makes it easier to troubleshoot.
    [post=13586]Quoted post[/post]​
    [/quote]
     
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