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ADS8902B: Sampling for lowest noise

larry baxter
Prodigy 70 points
Part Number: ADS8902B

I'd like to measure the amplitude of an amplitude-modulated 4V p-p 100kHz sine wave, at 18-20 bits resolution.  I could

1. Demodulate it to a 2V p-p rectified sine wave, lowpass filter, amplify, and sample at 200ksps, or

2. Sample synchronously at the peaks, at 200ksps, and demodulate digitally

Which is lower noise?  2) is simpler and would not have 1/f noise, but would total noise be lower?

Thanks!

  • 0
    TI__Mastermind 39710 points
    Hi Larry,

    Welcome to the TI E2E Community!

    The average of a rectified 4Vpp sine wave will be around 0.6V. Since you will amplify this in Option 1, this will likely result in the lowest overall total system noise. However, option 1 requires passing the signal through several stages which will each add additional noise, but with the proper selection of amplifiers and passives, this approach should give you the best overall resolution and lowest noise.

    I would not give up on option 2 since this is the easier approach. With digital processing and the high resolution of the ADS8902B, you may be able to hit your system target noise with this approach.

    Regards,
    Keith N.