Open-loop Software Automatic Gain Control: Common-mode Power-line Interference Stabilization During ECG Recording

Automatic gain control (AGC) units are widespread in modern telecommunication systems. The main function of AGC is to stabilize the amplitude of the processed signal. AGC generates a constant amplitude output signal when the input signal level changes. This article describes an all-digital architecture for automatic open-loop gain control designed to generate constant amplitude of the power-line interference extracted from the common-mode signal during ECG biopotential recording. The presented open-loop AGC has a very simple architecture and can be applied to other applications where AGC functionality is needed.