Magnetic field sensors and sensing circuits

A circuit for sensing an external magnetic field, comprising:

• a first voltage source for providing a power voltage;
• a first magnetic sensor for providing a reference current;
• a second magnetic sensor for sensing an external magnetic field, a conductivity of the second magnetic sensor varying in response to the external magnetic field;
• a bias voltage unit connected to the first magnetic sensor and the second magnetic sensor for providing a bias voltage to the first magnetic sensor and the second magnetic sensor,
• a clamp voltage current mirror unit for generating a reference current for the first magnetic sensor and mirroring the reference current to the second magnetic sensor;
• and
• a signal transfer amplifying unit for generating an output voltage and an additional current to compensate the change in the conductivity of the second magnetic sensor.

A method for forming a magnetic sensor, comprising:

• disposing a first magnetic tunneling junction and a second magnetic tunneling junction between a first electrode and a second electrode on a substrate, the first magnetic tunneling junction and the second magnetic tunneling junction being aligned along a first easy axis, the first magnetic tunneling junction including a first pinned layer, a first tunneling layer, and a first free layer, and the second magnetic tunneling junction including a second pinned layer, a second tunneling layer, and a second free layer;
• connecting the first magnetic tunneling junction and the second magnetic tunneling junction in parallel between the first electrode and the second electrode;
• setting a first pinned magnetization in the first pinned layer of the first magnetic tunneling junction and a second pinned magnetization in the second pinned layer of the second magnetic tunneling junction along a first pinned direction by subjecting the magnetic sensor to one or more external magnetic fields during an annealing process, the first and second pinned magnetizations each forming an angle of about 45 or 135 degrees with the first easy axis;
• and
• applying ampere fields to the first free magnetization in the first free layer of the first magnetic tunneling junction and the second free magnetization in the second free layer of the second magnetic tunneling junction by a setting current, the first and second free magnetizations being parallel to the first easy axis and in substantially opposite directions.