SBOS945B November 2020 – April 2021 INA849
PRODUCTION DATA
The stability and temperature drift of external gain setting resistor RG also affects gain. The contribution of RG to gain accuracy and drift is determined from Equation 1.
The best gain drift of 5 ppm/℃ (maximum) is achieved when the INA849 uses G = 1 without RG connected. In this case, gain drift is limited by the mismatch of the temperature coefficient of the integrated 5-kΩ resistors in differential amplifier A3. At gains greater than 1, gain drift increases as a result of the individual drift of the 3-kΩ resistors in the feedback of A1 and A2, relative to the drift of external gain resistor RG.
The low temperature coefficient of the internal feedback resistors improves the overall temperature stability of applications using gains greater than 1 V/V over alternate solutions.
The low resistor values required for high gain make wiring resistance an important consideration. Sockets add to the wiring resistance and contribute additional gain error (such as a possible unstable gain error) at gains of approximately 100 or greater.
To maintain stability, avoid parasitic capacitance of more than a few picofarads at the RG connections. Careful matching of any parasitics on the RG pins maintains optimal CMRR over frequency.