Abstract: Magnetometer circuits are disclosed in which a solenoidal sensor coil including a saturable core is provided a source potential to bring the coil towards saturation, followed by deactivation of the potential to the coil. The current through the coil is sensed and the magnetic field effecting the coil may be determined based on the amount of time which is required for the current in the coil to decline from a first level to a second level. A current sensor connected to the sensor coil provides a first output signal in response to the current through the coil increasing to a first value in a first portion of an operational cycle, and provides a second output signal in response to the current through the coil decreasing to a second value. The time period between the first and second output signals from the current sensor is indicative of the magnitude of the field affecting the coil.