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Thread: [EE] 24-bit A/D. Are We in the Twilite Zone Here?
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face BY : David VanHorn email (remove spam text)



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>Am I at the tradeoff point in my design? Is there some magical
>Noise-vs-??something??  formula here I forgot about [like trading
>gain for bandwidth]? Also, they are putting 16-bit sound cards
>into PCs nowadays. What the heck do those guys know, that they
>can accomplish that?

Begin at the beginning :)

Decouple your supplies into the op-amp.  A series R and local C to ground
should work well.

Check the op-amp PSRR AT the frequency of your main interference.

Use a spectrum analyzer to check everything, not just a scope.

Using a SMPS?, trigger the scope with the SMPS, and then go hunting noise
with the other input.

Make sure your local ground is quiet, and does not have someone else's
return current running through it. On my check reader board, I had two
700mA chopped stepper drivers less than an inch away, and got zero pickup
from that. Or the uP, or the SMPS. Un-measurable.

In the circuit itself, lower the impedances if you can, keep layout tight,
don't ground or decouple to any foreign points.

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Subject (change) [EE] 24-bit A/D. Are We in the Twilite Zone Here?

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