disclosed are circuits for automatic calibration of the gain of electronic amplification and digitization systems for use with x - ray detectors . the calibration is based on injecting predetermined pulses into the electronic system and deriving a calibration ratio based the digital value of their amplitude with the digital value of the same pulses , unamplified and digitized with a high accuracy reference adc . all adcs , as well as the dacs used to control the pulser amplitude are referenced to a single common reference voltage . calibration for non - linearity of the gain is disclosed with an alternative embodiment for the same circuits .