A physically unclonable function device includes a set of diode-connected MOS transistors having a random distribution of respective threshold voltages. A first circuit is configured to impose, on each first transistor, a fixed respective gate voltage regardless of the value of a current flowing in this first transistor. A second circuit is configured to impose, on each second transistor, a fixed respective gate voltage regardless of the value of a current flowing in this second transistor. A current mirror stage is coupled between the first circuit and the second circuit and is configured to deliver the reference current from a sum of the currents flowing in the first transistors. A comparator is configured to deliver a signal whose level depends on a comparison between a first current obtained from a reference current based on the first transistors and a second current of the second transistors.