ADS1256 Gain and Offset specs needed for buffer disabled mode

Hi Tony,

I would estimate the errors for the other PGA gains as follows...

• The offset error is on the level of the noise after calibration. Refer to table 4 to get the noise/offset error for the various PGA gains with the buffer disabled.
   
• The the offset drift will be somewhere between the gain = 1 and gain = 64 cases, because offset drift is an input-referred value that tends to get smaller as the gain increases. For example, the offset drift for gain = 2, is likely to be slightly larger than the offset at gain = 1 divided by 2.
   
• Gain error is only specified for the buffer enabled; however, as the buffer is another possible source of error, I would only expect the gain error to improve (or remain about the same) by taking the buffer out of the input signal path. The gain error for the other gains will likely be in range of the gain = 1 and gain = 64 cases.

...This assumes that the input signal source has a low output impedance! The source's output impedance and ADC's input impedance may create a resistor divider effect that causes an additional gain error when the source's output impedance is high.
 

• Gain error drift appears to be constant for gain = 1 and gain = 64. I would expect similar performance for all gains.
   

Best Regards,
Chris