Automatically calibrating operational amplifier (op-amp) systems for mitigating effects of offset voltages are disclosed. In one aspect, an automatically calibrating op-amp system is provided that employs an analog calibration signal corresponding to a calibration mode to compensate an output voltage signal of an op-amp corresponding to an amplify mode. An automatic calibration circuit is included that employs a successive approximation register (SAR) controller configured to successively generate digital values based on the output voltage signal of the op-amp in response to a mode signal indicating the calibration mode. The automatic calibration circuit includes a digital-to-analog converter (DAC) configured to convert each successive digital value into the analog calibration signal in response to the mode signal indicating the calibration mode. The analog calibration signal is provided to an auxiliary differential input of the op-amp to compensate for the composite offset voltage in the amplify mode.