An amplifier having at least one switch controlled by an output voltage of a hysteresis block, wherein the hysteresis block is adapted to receive an input voltage signal based on an integration of an error signal, a low threshold voltage and a high threshold voltage, and is arranged to change the output voltage from a first value to a second value when the input voltage signal is higher than the high threshold voltage and to change the output voltage from the second value to the first value when the input voltage signal is lower than the low threshold voltage, and wherein the low threshold voltage is equal to Vref−αVDD and the high threshold voltage is equal to Vref+αVDD, where Vref is a common mode voltage level, α is a non-zero constant, and VDD is a power supply voltage.