7.3.1.1 Gain Drift

The stability and temperature drift of the external gain setting resistor, R_G, also affects gain. The contribution of R_G to gain accuracy and drift can be determined from Equation 1.

The best gain drift of 5 ppm/℃ (maximum) can be achieved when the INA828 uses G = 1 without R_G connected. In this case, gain drift is limited only by the slight mismatch of the temperature coefficient of the integrated 40-kΩ resistors in the differential amplifier (A₃). At gains greater than 1, gain drift increases as a result of the individual drift of the 25-kΩ resistors in the feedback of A₁ and A₂, relative to the drift of the external gain resistor R_G. The low temperature coefficient of the internal feedback resistors significantly improves the overall temperature stability of applications using gains greater than 1 V/V over alternate solutions.

Low resistor values required for high gain can make wiring resistance important. 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 assure stability, avoid parasitic capacitance of more than a few picofarads at R_G connections. Careful matching of any parasitics on both R_G pins maintains optimal CMRR over frequency; see Typical Characteristics, Figure 17.