Abstract: An operational amplifier including an input stage coupled to an input terminal, an output stage coupled to an output terminal, and a gain node between the input stage and the output stage. A bias current source is couplable to the input stage to supply a bias current thereto and a current mirror circuit mirrors the bias current toward the gain node and the output stage. A switch circuit includes a switch activatable to bring the gain node to a pre-bias voltage and a switch coupled to the output stage and switchable between a first state and a second state in which the output stage is active and non-active, respectively—. A further switch circuit is coupled to the output terminal and switchable between a first state and a second state in which the output stage is coupled to the output terminal and to a reference level, respectively.