INA851: Instrumentation amplifier

HI Dibin,

It is possible to feed a 20Vpp signal into the positive input terminal, while grounding the input terminal.  

The INA851 input stage can be set on G=+1 V/V, by keeping RG unpopulated, and the output stage can be configured on G=0.2 V/V by shorting G02+ to OUT+ and G02- to OUT- providing accurate results.  

It may be possible to place a 417Ω resistor between G02+ to OUT+ and G02- to OUT- to obtain Gain around ~ 0.25V/V, however, but keep in mind, this will cause gain accuracy errors due to the mismatch in absolute value and drift of the external resistors, vs the absolute value and drift of the internal resistors. The INA851 R1-R6 output stage internal gain resistors are ratiometrically matched among each other, to provide low gain error and very low gain error drift; but their drift and absolute value will not be matched to an external resistor, causing gain error and gain drift error.  Although the internal resistors of the output stage are precisely matched among each other, their absolute value could vary up to ±15% over process variation and temperature.

Assuming that the 20V peak-to-peak (Or 10Vpeak) input signal is centered around GND, and the input stage is powered with bipolar supplies VS+/VS- of at least ±12.5V or greater, the device can accommodate the input signal. 

Let me know if the DC level of the input signal is not centered around GND.

Thank you and Regards,

Luis