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OPA827: slau522_TI Precision Designs Verified Design

LEE WOONG-HEE
Prodigy 30 points
Part Number: OPA827

Tool/software:

Hello.
I have a question about the document below.
"slau522_TI Precision Designs Verified Design"

First
Please check the error in the document below.
2.1 Detailed Schematic
- 0.1Hz LPF(HPF) 2nd order G = 10
- 10Hz HPF(LPF) 2nd order G = 10
- 10Hz HPF(LPF) 2nd order G = 1

Second
In the document, it is guided as +15V, -15V.
What is the difference when designing with +5V, 0V(GND)?
In other words, how does the result change depending on the voltage?

Thank you.

slau522_TI Precision Designs Verified Design.pdf

  • 0
    TI__Mastermind 23668 points

    Lee,

    1. You are correct.  The red text on figure 3 is labeled incorrectly.  The term HPF and LPF are swapped.  The first stage is a HPF, and the next two stages are LPF.
    2. Regarding using the circuit for a 5V supply:
      1. The easiest thing to do would be to use +/-2.5V.  If you do this the circuit would not require any modifications.  The key point is that the amplifier needs to be in a linear operating state. In other words, you cannot violate the common mode range or output swing limits.  If you keep the circuit as is and apply Vss = 0V, and Vcc = +5V, than the amplifier common mode range and/or output swing will be violated and the amplifier will be driving into the rail.  If you use a +/-2.5V supply the noise will be the same as with a 0V and 5V supply but the common mode and output swing will be in the middle of the range.
      2. Alternatively, you could use a 0V and 5V supply but you would have to apply 2.5V to all the ground locations.  This is basically the "single supply" configuration.  This is not a good approach as the 2.5V supply will likely have noise and this will impact your measurement.
    3. Thanks for pointing out the error.  I will put this on my list of correction.  Sorry for the confusion.
    4. Bellow is a TINA schematic for the filter.  You can simulate the transfer characteristic to prove the circuit operation.

    p1-to10Hz.TSC

    Best regards, Art

  • 0 in reply to Art Kay
    Prodigy 30 points

    Hi.
    Thank you for your reply.
    I will test it and reply.
    Thank you.

  • 0 in reply to LEE WOONG-HEE
    TI__Mastermind 23668 points

    Happy to help, Art

  • 0 in reply to Art Kay
    Prodigy 30 points

    Hi.

    I have additional questions.

    I am using a +-2.5V power supply and plan to apply it to a medical device.

    Can you recommend some components for the power configuration?

    Thank you.

  • 0 in reply to LEE WOONG-HEE
    TI__Mastermind 23668 points

    Lee,

    I think you want me to recommend an LDO or a DC-to-DC power device.  I really don't support these devices, so I am not familiar with the latest-and-greatest options.  You should post on the power forum.  They are very familiar with the devices and can suggest the best options.

    Best regards, Art

  • +1 in reply to Art Kay
    Prodigy 30 points

    Thanks for your reply.
    I will ask the power forum.
    Thank you.