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LDO input-output characteristic problem

Discussion in 'Mathematics and Physics' started by anhnha, Apr 21, 2014.

  1. anhnha

    anhnha Member

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    Hi.
    Please help me solve the problem with my LDO in the picture below. Thank you.

    [​IMG]
     

    Attached Files:

    Last edited: Apr 21, 2014
  2. ronsimpson

    ronsimpson Well-Known Member Most Helpful Member

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    I need more information.
    Part numbers.
    What is Vbg? How is this voltage made?
    Power supply pins on op-amp?
    Resistor values?
    Where are the capacitors?
    Load current?
     
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  3. anhnha

    anhnha Member

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    Thank you.
    I simulated the circuit in Cadence using TSMC 180nm.
    I used a bangap circuit with Vbg = 0.8V.
    It is relatively good.
    Opamp is powered from Vin (2 to 3.3V)
    Top resistor: 100K
    Bottom resistor: 80K.
    Cload = 1pF.
    I didn't measure it. But Rload = 180Ohms and therefore, Iload = 0.01A.
     
  4. dave

    Dave New Member

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  5. ronsimpson

    ronsimpson Well-Known Member Most Helpful Member

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    So the op-amp is powered from Vdd, the same as on the source of the MOSFET.
    What op-amp are you using? I need to know input range. If you give a part number I can find the numbers I am looking for.
    What MOSFET are you using? I need to know gate turn on voltage. N or P?
    Please plot Vdd and Vout, Gate of MOSFET. I want to see the output of the opamp.
     

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