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INA827: Noise

user5981663
Prodigy 65 points
Part Number: INA827

Rg= 80ohm, Vpower=8V.

Without any input signal (Granded for both -IN, +IN) there is almost 22mVpp on output.

No appearently noise on Vdd.

What kind of things I have to concern to reduce more output noise.

BEST REGARDS,

Hironari

  • 0
    Guru 140200 points
    Hi Hironari,

    can you show a schematic?

    Kai
  • 0
    TI__Guru 64840 points

    Hironari,

    The broadband input noise may be calculated using following formula: 

    Where ebb is the broadband voltage noise spectral density and BWn is the noise bandwidth.  Since in case of INA827, ebb is 18nV/rt-Hz and BW for the gain of 1000 is specified to be 15kHz, Enbb=18nV*(15,000*1.57)^0.5 = 2.76uVrms (1/f noise contribution is small and may be neglected).  Reflecting the input noise to the output using gain, G=5+80k/80=1005, results in Vonoise=1005*2.76uV=2.8mVrms, which translates into Voutpp = 6.6*2.8=18.3mVpp (very close to 22mVpp you see) - increase of bandwidth due to process variation, EMI interference and/or supply noise may account for the small difference.  Therefore, the only way to significantly decrease the output noise in your system is by either decreasing the gain or by placing a low pass filter, with fc<15kHz, at the output of INA827.