The magnetic field sensor is composed of a semiconductor magnetic field sensor, for example a magnetotransistor, and at least one NiFe or NiCo film disposed upon its surface. This film functions as a zero-crossing switch utilizing its magnetic induction/magnetic field-reversal hysteresis properties. The film is deposited immediately above the field sensitive zone of the magnetic field sensor with its easy axis oriented perpendicularly to the direction of current flow of the sensor. The semiconductor magnetic field sensor detects the magnetic induction generated by the film.