Stability Parameter
The rate at which the input offset voltage of an amplifier changes in response to fluctuations in the average voltage applied to both inputs defines this metric. Low common mode voltage drift is necessary for precision instrumentation used in bridge measurements and high side current sensing. Manufacturers specify this value in microvolts per volt to describe the rejection capability over the full operating range.
Thermal Influence
Internal component matching degrades as temperatures shift leading to a varying offset. Even a highly symmetrical circuit experiences common mode voltage drift due to non linearities in the input stage transistors.
Error Accumulation
Unwanted signal shifts caused by this phenomenon introduce measurement uncertainty that cannot be easily distinguished from the actual input signal. In systems where the common mode voltage varies widely, such as a battery stack monitor, the resulting drift limits the achievable resolution. Digital calibration can remove static offsets but fails to track the dynamic changes occurring during operation.
Calibration Bound
Laboratory verification requires a stable voltage source and a high resolution voltmeter to characterize the amplifier across its entire input swing. Technicians measure common mode voltage drift by recording the offset change at multiple discrete steps while maintaining a constant ambient temperature. The specification holds only when the device operates within its linear common mode range as defined by the power supply rails.
