Magnetic field sensor including a magnetic field sensing circuit (2) comprising a reference magnetic field generator (8) and a magnetic field sensing cell (6), and a signal processing circuit (4) connected to the output of the magnetic field sensing cell and comprising a demodulator circuit and a gain correction feedback circuit (30, 28, 47) for correcting error fluctuations in the transfer characteristic of the magnetic field sensor. The sensor further comprises a reference current generator (3) configured to generate a reference current I ref, the reference current generator connected to the magnetic field sensing circuit (2) configured for generating the reference magnetic field B ref and to the gain correction feedback circuit configured for providing a reference signal (yref) to which an output signal of the demodulator circuit may be compared.