An amplification circuit includes an amplifier circuit (provided by an operational amplifier) that amplifies a signal to be demodulated. A feedback loop of the amplification circuit has a resistance value that is controlled to discretely vary according to a level of an output node of the amplifier circuit. A comparison of the output level with respect to one or a plurality of thresholds, which define out-of-saturation operating ranges of the amplifier circuit, drives selection of the resistance value.