A magnetic field sensor for measuring a direction of a magnetic field in a plane comprises a sensing structure (4) comprising a ring-shaped well (10), a plurality of contacts (11) of equal size placed at equal distance from each other along the ring-shaped well, and an electronic circuit (5) comprising a plurality of electronic switches (12) associated with the contacts (11) of the sensing structure (4), a logic block (18) for controlling the electronic switches (12), at least one current source (13; 14), a means for measuring a difference between a first voltage and a second voltage, a timing circuit providing a control signal for controlling the logic block (18) and providing a reference signal, wherein the logic block is adapted to close and open the electronic switches under the control of the control signal according to a predetermined scheme such that a predetermined number of contacts of the plurality of contacts form a vertical Hall element that is supplied with current from the at least one current source and that has two contacts connected to the means for measuring, and such that the vertical Hall element is moved in steps along the ring-shaped well, and a means for measuring a phase shift between the reference signal and an output signal of the voltage measuring means.