Amplifier and control method thereof

摘要

An amplifier (1) is arranged to amplify a sense signal from a sensor with low current consumption while maintaining sufficient sensitivity. The amplifier (1) comprises a detection circuit (2) which detects a signal level of the sense signal and outputs an alarm signal when the sense signal is in a first signal level range, and a variable gain amplifier (3) which, based on a detection result of the detection circuit (2), stops an amplifying operation when the sense signal is in the first signal level range, performs the amplifying operation at a first gain when the sense signal is in a second signal level range, or performs the amplifying operation at a second gain larger than the first gain when the sense signal is in a third signal level range defined between the first and second signal level ranges.