A switched operational amplifier with fully differential topology, alternately switchable on and off, and a control circuit. The operational amplifier has a first differential output (4a) and a second differential output, and a control terminal. The control circuit includes a capacitive detecting network including a first capacitor and a second capacitor connected between the first and second differential outputs and a common-mode node, and a third capacitor connected between the common-mode node and ground in a first operative condition, and between the common-mode node and the supply voltage in a second operative condition. A control transistor is connected between the common-mode node and the control terminal of the operational amplifier and supplies a control current correlated to the voltage on the common-mode node. A switchable voltage source, connected to the common-mode node, supplies a desired voltage in a first operative condition, when the operational amplifier is off.