Auto-gain correction and common mode voltage cancellation in a precision amplifier

摘要

Auto-gain correction in a precision amplifier provides continuous calibration of the gain of the two differential input stages relative to each other and thus significantly minimizes the effects of device mismatch and temperature. Auto-gain correction together with auto-zero minimizes the effects of common mode input voltage on the amplifier and eliminates the need for trim associated with the matching of the two differential input stages. Improved gain matching enhances the accuracy of the auto-zero, which further improves the accuracy of auto-gain correction, resulting in a synergy with both operating together. The implementation of the auto-zero using an input pair of series capacitors in conjunction with a common input reference and a feedback pair of series capacitors in conjunction with a common feedback reference provides for decoupling the common mode voltage of the input differential pair or feedback differential pair. Various features may be used in sub-combinations as desired.