A Physical Unclonable Function, PUF, apparatus is disclosed. The apparatus comprises a plurality of PUF cells that each comprise a first potential divider and a second potential divider. The apparatus also comprises a determination unit that comprises a selection unit for selecting at least one of the plurality of PUF cells, and a readout unit coupled to each selected PUF cell. The readout unit is configured to determine a PUF value for the selected PUF cell based on a difference between a first analog voltage at the first potential divider and a second analog voltage at the second potential divider.