Linear bridge having nonlinear elements for operation in high magnetic field intensities
In one aspect, a bridge includes a first magnetoresistance element having a first reference angle; a second magnetoresistance element in series with the first magnetoresistance element and having a second reference angle; a third magnetoresistance element in parallel with the first magnetoresistance element and having the first reference angle; and a fourth magnetoresistance element in series with the third magnetoresistance element and having the second reference angle. An output of the bridge has a linear response over a range of horizontal magnetic field values having non-zero values and the range of horizontal magnetic field intensity values are associated with vertical magnetic field intensity values having zero Oersted (Oe) values. A reference angle indicates an angle the magnetoresistance element is most sensitive to changes in a magnetic field.
1. A bridge comprising:
a first magnetoresistance element having a first reference angle;
a second magnetoresistance element in series with the first magnetoresistance element and having a second reference angle;
a third magnetoresistance element in parallel with the first magnetoresistance element and having the first reference angle; and
a fourth magnetoresistance element in series with the third magnetoresistance element and having the second reference angle,
wherein an output of the bridge has a linear response over a range of horizontal magnetic field values having non-zero values,
wherein the range of horizontal magnetic field intensity values are associated with vertical magnetic field intensity values having zero Oersted (Oe) values,
wherein a reference angle indicates an angle the magnetoresistance element is most sensitive to changes in a magnetic field.
2. The bridge of claim 1 , wherein the first, second, third and fourth magnetoresistance elements are each a giant magnetoresistance (GMR) element or a tunnel magnetoresistance (TMR) element.
3. The bridge of claim 1 , further comprising:
a fifth magnetoresistance element in series with the first magnetoresistance element and having a third reference angle; and
a sixth magnetoresistance element in series with the third magnetoresistance element and having the third reference angle.
4. The bridge of claim 3 , wherein the fifth magnetoresistance element and the sixth magnetoresistance element are constructed to be the same.
5. The bridge of claim 4 , wherein the fifth magnetoresistance element and the sixth magnetoresistance element are constructed with the same pillar count.
6. The bridge of claim 5 , wherein the pillar count of each of the first, second, third, fourth, fifth and sixth magnetoresistance elements and the first, second and third reference angles are selected to enable the bridge to generate a linear output with a controlled offset over a temperature range from −10° C. to 100° C.
7. The bridge of claim 1 , wherein the first reference angle and the second reference angle enable the output of the bridge to have the linear response over the range of horizontal magnetic field intensity values having non-zero values.
8. The bridge of claim 7 , wherein the first reference angle and the second reference angle enable the output of the bridge to have the linear response over the range of horizontal magnetic field intensity values none of which have zero values.
9. The bridge of claim 1 , wherein the first magnetoresistance element and the third magnetoresistance element are constructed to be the same.
10. The bridge of claim 9 , wherein the first magnetoresistance element and the third magnetoresistance element are constructed with the same pillar count.
11. The bridge of claim 10 , wherein the second magnetoresistance element and the fourth magnetoresistance element are constructed to be the same.
12. The bridge of claim 11 , wherein the second magnetoresistance element and the fourth magnetoresistance element are constructed with the same pillar count.
13. The bridge of claim 1 , wherein the linear response is over a range that includes horizontal magnetic field values no less than 200 Oe.
14. The bridge of claim 13 , wherein the linear response is over a range that includes horizontal magnetic field values no less than 300 Oe.
15. The bridge of claim 13 , wherein the bridge has the linear response over a temperature range from −10° C. to 100° C.
16. The bridge of claim 1 , wherein the first reference angle is about perpendicular to the second reference angle.
17. The bridge of claim 16 , wherein the first reference angle is about perpendicular to a magnetic field for the sensor to sense.
18. A camera, comprising:
a magnetic field sensor comprising a bridge, the bridge comprising:
a first magnetoresistance element having a first reference angle;
a second magnetoresistance element in series with the first magnetoresistance element and having a second reference angle;
a third magnetoresistance element in parallel with the first magnetoresistance element and having the first reference angle; and
a fourth magnetoresistance element in series with the third magnetoresistance element and having the second reference angle,
wherein an output of the bridge has a linear response over a range of horizontal magnetic field intensity values having non-zero values,
wherein the range of horizontal magnetic field intensity values are associated with vertical magnetic field intensity values having zero Oersted (Oe) values,
wherein a reference angle indicates an angle the magnetoresistance element is most sensitive to changes in a magnetic field.
19. The camera of claim 18 , wherein the camera is disposed in a cellular device.
20. The camera of claim 18 , further comprising:
a magnetic target;
a focus controller;
a lens;
wherein a movement of the magnetic target is detected by the magnetic field sensor to provide an output to the focus controller to change the focal length of the lens.