Apparatuses, circuitry, architectures, systems, methods, algorithms and software for performing automatic gain calibration on an input signal. The apparatuses and/or circuits generally include an amplifier, a filter, a comparator, and a controller. The amplifier is configured to receive a gain level signal and to amplify the input signal in accordance with the gain level signal to produce an amplified signal. The filter is configured to filter the amplified signal to produce a filtered signal. The comparator is configured to compare the filtered output to a threshold value and to produce a comparison signal in response thereto. The controller is configured to iteratively reset the filter and adjust the gain level signal in response to the comparison signal to select a gain level. Embodiments of present invention advantageously provide for rapid automatic gain control, and are particularly advantageous for automatic gain control in systems adapted for input signals with bursting data and/or widely varying input amplitudes and/or in systems with a relatively large number of possible gain levels.