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ADS1281-EVM, 1/f-noise of OPA1632

Karl Zeilhofer
Prodigy 10 points
Other Parts Discussed in Thread: ADS1281, OPA1632, OPA2188, OPA188

Hello,

I'm using a ADS1281-EVM for a high-precision weighing scale, using electromagnetic force compensation.

The samples from the ADS1281 with 250S/s are downsampled to 1S/s. Therefore our interesting frequency band is from about 0.01Hz to 0.5Hz.

In this range the input amplifier (with the external componentes) used in the eval-module has a noise voltage of about 100nV! This is much more than I will expect from the analog circuit, which should be measured with the ADC.

For the analog circuit of the scale I'm using the Zero-Drift OP from Analog Devices (ADA4528-1), which has no 1/f-noise.

Do you have any suggestions for a replacement of the OPA1632, which has no 1/f-noise? In best case is will also have the same footprint, so i can replace it on the EVM.

kind regards,

Karl Zeilhofer

  • 0
    TI__Mastermind 44670 points

    Hello Karl,

    Welcome to the TI E2E forums!

    Any chopping or auto-zero amplifer will have practically zero 1/f noise. See the OPA188 or dual version OPA2188.

    The downside of using the OPA188 or ADA4528-1 is that they are not of the differential output type, like the OPA1632. However, you could build a fully differential amplifier using the dual OPA2188.

    Note: The OPA188, OPA2188, and OPA1632 have the similar packages but different pinouts.

    Regards,
    Chris