SBOA571 august   2023 OPA2387 , OPA387 , OPA4387

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Introduction
  5. 2Example Considerations
  6. 3Introducing a Preconditioning Circuit
    1. 3.1 First Order Shelving Filter
    2. 3.2 Second Order Shelving Filter
    3. 3.3 Noise Contribution of the Second Order Shelving Filter
    4. 3.4 DC and AC Gain
  7. 4Design Procedure for the Second Order Shelving Filter
    1. 4.1 Definition of Boundary Conditions
    2. 4.2 Calculation of Component Values
  8. 5Influence of Component Tolerances
  9. 6Summary
  10. 7References

3.4 DC and AC Gain

With the additional gain in the DC (+18 dB) and AC (+4.54 dB) bands, the ADC input receives a DC value of 160 uV and an AC value of 37.125 mV. With a PGA gain of 32, the DC value compared to the 1.2-V VREF results in +/-5.12 mV and the AC value reaches full scale +/-1.2 V.

GUID-20230802-SS0I-MZ7W-MNKQ-BXJQN5RHVN97-low.pngFigure 3-11 FFT DC in AC With PGA Gain = 32 and Filter Correction, VREF = 1.2 V