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Original question:

PGA900: PSRR of PGA900 AVDD and bridge supply

PGA900: How to reduce output voltage noise of PGA900?

hao Su
Intellectual 560 points
Part Number: PGA900
Other Parts Discussed in Thread: OPA2182, , OPA187

Tool/software:

Hi:

We have a project for SG bridge application which need output voltage noise be smaller than 1mv  at 0.5v output.

I add a per-amplifier OPA2182 before PGA900 and OPA187 before the PGA900.

The PGAIN of PGA900 is 50x. PGA900 was set to radiation output. 

But output signal noise is about 1.7mV now, Could you give me some suggestions for reduction the noise?

Here are picture of schematic.

  • 0
    TI__Intellectual 2555 points

    Hi Hao Su, 

    I have a couple of questions:

    • What is the PGA900 power supply? Is it linear regulators or switching regulators?
    • What is the purpose of the amplifier on the input? What is your input range?
    • What is the purpose of the amplifier on the output? What is your output range from PGA900?

    Thanks,

    Maggie

  • 0 in reply to Maggie Lee
    Intellectual 560 points

    Hi Maggie:

    1. We use low noise DC supply, but no power regulator because we use OWI calibration.

    2. The amplifier is used for reduce output noise, input signal is come from SG bridge , about 1mv/V

    3. The amplifier on the output are also design for reduce output noise

  • 0 in reply to hao Su
    TI__Guru 53636 points

    Hi hao Su,

    Maggie is out of the office due to the US holiday on Monday, please expect a reply early next week. Thanks for your patience

    -Bryan

  • 0 in reply to hao Su
    TI__Intellectual 2555 points

    Hi Hao Su, 

    Please refer to these videos for calculating the noise of an amplifier-ADC signal chain: video 1 video 2

    It's possible the external amplifier on the ADC input is adding more noise than you anticipated. 

    What is your output range? Do you really need an output amplifier? The PGA900 DAC can produce a 0-10V signal. You may be adding more noise with an output amplifier.  

    Thanks,

    Maggie