Hi, One thing that may affect the output of the PGA is the input range of the PGA itself. The PGA is constructed like the input of an instrumentation amplifier. First, note that if the supply is unipolar (from 0V to 5V). The input should not be grounded. The input does not extend to ground, because like an amplifier, the output can't be pulled all the way to either rail. Also, the input signal common mode must be the same as the output signal common mode of the PGA. The input range will be more limited as the gain gets higher. If you go to the ADS1248 datasheet, the PGA and the PGA input range is discussed in detail starting on page 26. Let me know if this clears up your PGA problem. Joseph Wu
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