INA181-Q1: Question about input filtering

Tsuyoshi Nogi

Intellectual 1970 points

Part Number: INA181-Q1

Tool/software:

Hi experts,

Our customer want to cut noise by reducing cutoff frequency(fc) of input R-C filtering.

there is a 2 ways to reduce fc; increasing Rf or increasing Cf.

I saw that by increasing Rf, the gain error increase as on D/S 8.1.3.

However I couldn't find the statement about the side effect occurred by increasing Cf.

Questions,

could you share the effect occurred by increasing Cf?

Are there any way to reduce cutoff frequency?

Thanks and regards,

Tsuyoshi

3 months ago

+1 Clemens Ladisch 3 months ago

Guru 311870 points

The gain error is measured for DC signals, and Cf has no effect on DC signals.

(Larger electrolytic capacitors have a larger leakage current, but I guess you're not using those.)

0 Tsuyoshi Nogi 3 months ago in reply to Clemens Ladisch

TI__Intellectual 1970 points

Hi Ladisch-san,

Thank you for your comments!

How about the effect for AC signals?

and are there any effect for anything other than gain error?

Thanks and regards,

Tsuyoshi

+1 Clemens Ladisch 3 months ago in reply to Tsuyoshi Nogi

Guru 311870 points

You get gain errors only for Rf. (The four internal resistors are precisely matched; adding Rf has the same effect as increasing the resistors labelled "Rint".)

Cf slows down changes in the input signals. As far as the INA181-Q1 is concerned, this simply filters out high frequencies.

0 Joe Vanacore 3 months ago in reply to Clemens Ladisch

TI__Genius 15790 points

Thank you for your inputs Clemens :)

Hello Tsuyoshi,

I believe Clemens answered your questions but please respond with any additional questions you may have.

Best Regards,

Joe

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INA181-Q1: Question about input filtering