A magnetometer is disclosed that enables high resolution magnetometry using magnetoresistive sensors that consume less power. The magnetometer exploits the ability of the sensor to alter or modulate sensitivity via external means. This modulation effectively transfers the signal of interest from the noisy DC domain to the AC domain by applying an AC signal to a current strap in a magnetic field sensor. The AC signal causes a first magnetic field to be formed in a direction perpendicular to the current strap. A magnetic field sensing structure in the magnetic field sensor senses the first magnetic field. The magnetic field sensing structure uses the first magnetic field to sense a second magnetic field. The second magnetic field is an external magnetic field that is of interest. An output of the magnetic field sensing structure is an AC signal that is proportional to the second magnetic field. The AC signal may be further amplified and refined employing signal conditioning techniques.