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OPA2991: Please review the schematic

Part Number: OPA2991

Dear TI experts,

My customer drew their own schematic with OPA2991. Could you review this schematic?

++ OPA_VCC+ and OPA_VCC- are 5V~20V variable.

++ DAC0_OUT and DAC1_OUT are 3.3V.

++ the voltage of OPA_OUT+ and OPA_OUT- are related to OPA_VCC+ and OPA_VCC-. (5V~20V variable.)

Best regards,


  • Hi Chase,

    I rearranged the circuit. See below to double check if I got anything wrong. 

    I'm still checking the stability analysis of the circuit and will get back to you soon.

    Best Regards,

    Robert Clifton

  • Hi Chase,

    Are all the resistor values going to be 100kohm? 

    The reason I ask is due to the first stage op amp's stability being affected by the 100kohm. Please note that the 10pF load is coming from the input capacitance of the second stage op amp. 

    When I ran the stability analysis I saw only 28.11 degrees of phase margin. 

    This can be counteracted by lowering the 100kohm resistor to the non-inverting input pin to be 1kohm, which gets you to 41.58 degrees, which is a little lower than the recommended 45 degrees of phase margin we recommend. 

    Alternatively you can add a 10pF to the input and get about 49 degrees of phase margin.

    Best Regards,

    Robert Clifton