Magnetoresistance bridge circuits with stray field immunity

A magnetic field sensor system comprising:

• a first bridge comprising a first magnetoresistance (MR) element, a second MR element, a third MR element, and a fourth MR element, wherein the first MR element is coupled between a power source and a first output node, the second MR element is coupled between the power source and a second output node, the third MR element is coupled between the second output node and ground, and the fourth MR element is coupled between the first output node and ground;
• a second bridge comprising a fifth MR element, a sixth MR element, a seventh MR element, and an eighth MR element, wherein the fifth MR element is coupled between the power source and a third output node, the sixth MR element is coupled between the power source and a fourth output node, the seventh MR element is coupled between the fourth output node and ground, and the eighth MR element is coupled between the third output node and ground;
• and
• wherein the first bridge is positioned to sense a first uniform magnetic field of a first polarity and wherein the second bridge is positioned to sense a second uniform magnetic field of a second polarity opposite to the first polarity, wherein the first uniform magnetic field and the second uniform magnetic field are generated by a common magnetic field source and have equal magnitudes;
• and
• wherein the first bridge and the second bridge are coupled in parallel to form a parallel bridge circuit with the first output node connected to the third output node at a first output of the parallel bridge circuit and with the second output node connected to the fourth output node at a second output of the parallel bridge circuit.

A magnetic field sensor comprising:

• a composite bridge comprising a first magnetoresistance (MR) element and a sixth MR element coupled in series to form a first bridge leg between a power source and a first output node, a second MR element and a seventh MR element coupled in series to form a second bridge leg between the power source and a second output node, a third MR element and an eighth MR element coupled in series to form a third bridge leg between the second output node and ground, and a fourth MR element and a fifth MR element coupled in series to form a fourth bridge leg between the first output node and ground;
• wherein each of the first MR element, the third MR element, the fifth MR element, and the seventh MR element has a first magnetic reference direction;
• and
• wherein each of the second MR element, the fourth MR element, the sixth MR element, and the eighth MR element has a second magnetic reference direction that is opposite with respect to the first magnetic reference direction.