A gain circuit comprises a main amplification unit and a first refresh unit. The main amplification unit comprises an amplifier, a first capacitor connected between a first input terminal of the gain circuit and a first input terminal of the amplifier, and a second capacitor connected between the first input terminal of the amplifier and a first output terminal of the amplifier. The first refresh unit comprises a first capacitor connected with a first terminal of the first capacitor to a common node of the first refresh unit, and a second capacitor connected with a first terminal of the second capacitor to the common node of the first refresh unit. The common node of the first refresh circuit is arranged to be supplied with a reference voltage (Vref, Vcm,ref) during a first phase of a refresh interval and connected to the first input terminal of the amplifier during a second phase of the refresh interval.