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

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>Sounds like you could use some front-end RF filtering too. Maybe
>ferrite beads in the input signal lines, or inductors in the Vcc
>lines, etc.

BTDT. None of that made a noticable difference without changing the op-amp.
I'm going in again now, and re-evaluating all that in case it makes a
difference, but it was too small to observe before.

>And I've looked at dozens of op amp specsheets in the past couple
>of days. Turns out all of the JFET types have very bad PSRR- at 1
>Mhz, only 0 to 20 dB. Even true for Natl LM6152 which is 75 Mhz GBW.

Use the best you can afford, and then fix as much as possible on the layout.
RC filters specifc to the op-amp will help a lot, they will knock 1 MHz
right down.
Those Murata/Panasonic EMI filters are great down there, and cheap too $0.25.

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

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