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Design >> Analog Design >> architecture trade off on input loading of sigma-delta ADC
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Message started by neoflash on Oct 9^th, 2017, 10:34am

Title: architecture trade off on input loading of sigma-delta ADC
Post by neoflash on Oct 9^th, 2017, 10:34am

In order to get best performance on tiny input signal, the pre-amp gain will be adjusted to properly load the trailing 20-bit sigma-delta ADC.

However, the high gain of pre-amp will introduce distortion. Give the lower speed operation, system may prefer to have a lower gain at preamp and let sigma-delta adc work harder to get the performance.

For nyquist adc, it is highly undesired to load adc very lightly, we are very motivated to load ADC near full DR.

What is the considerations for oversampling ADC in this case?

Thanks,
Neo

Title: Re: architecture trade off on input loading of sigma-delta ADC
Post by Frank_Heart on Nov 17^th, 2017, 10:57pm

Hi, Neo,

I think it should be similar. We always want the pre-amp gain to be as large as possible to degrade ADC noise, referring to input. Of course, the degraded linearity should be within spec, if it is for wide band applications.

Regards,
Frank