# US 2017/0285117 A1 · Magnetic Field Sensor and Electronic Circuit That Pass Amplifier Current Through a Magnetoresistance Element

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- Number: US 2017/0285117 A1
- Document ID: US20170285117A1
- Status: Published application
- Kind: A1
- Application number: 15/624,898
- Filed: 2017-06-16
- Published: 2017-10-05
- Earliest claimed: 2014-10-31
- Assignees: Allegro MicroSystems, LLC
- Applicants: Allegro MicroSystems, LLC
- Inventors: Mathew Drouin; Devon Fernandez; Jay M. Towne; Alejandro Gabriel Milesi
- Web page: https://patentgrep.com/patent/US20170285117A1

## CPC

- G01R 33/09: Magnetoresistive devices
- G01R 33/0023: {Electronic aspects, e.g. circuits for stimulation, evaluation, control; Treating the measured signals; calibration (G01R33/0017 takes precedence)}
- G01R 33/028: Electrodynamic magnetometers
- G01R: MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES (indicating correct tuning of resonant circuits H03J3/12)

## Abstract

Electronic circuits used in magnetic field sensors use transistors for passing a current through the transistors and also through a magnetoresistance element.

## Claims

### Claim 1

An electronic circuit coupled to receive a power supply voltage, comprising:
a first magnetoresistance element having first and second terminals;
a first transistor having a control node, a first current passing node, and a second current passing node; and
a first voltage generating source having first and second nodes between which a first fixed voltage is generated, wherein the first terminal of the first magnetoresistance element is coupled to the first current passing node of the first transistor, wherein the control node of the first transistor is coupled to receive the first fixed voltage, and the second node of the first voltage generating source is coupled to the second terminal of the first magnetoresistance element, wherein the electronic circuit is operable to generate a first current signal at the second current passing node of the first transistor related to a resistance value of the first magnetoresistance element.

### Claim 2 (depends on 1)

The electronic circuit of claim 1, further comprising a fixed resistor having first and second terminals, the first terminal of the fixed resistor coupled to the second current passing node of the first transistor, wherein the fixed resistor is operable to pass the first current signal and convert the first current signal to a voltage signal at the second current passing node of the first transistor.

### Claim 3 (depends on 1)

The electronic circuit of claim 1, wherein the first voltage generating source comprises a reference leg of a current mirror circuit.

### Claim 4 (depends on 1)

The electronic circuit of claim 1, further comprising:
a comparator coupled to the second current passing node of the first transistor for generating a two state output signal.

### Claim 5 (depends on 1)

The electronic circuit of claim 1, further comprising:
a first fixed resistor having first and second terminals;
a second transistor having a control node, a first current passing node, and a second current passing node;
a second voltage generating source having first and second nodes between which a second fixed voltage is generated; and
a first load coupled to the second current passing node of the first transistor, wherein the second current passing node of the first transistor is coupled to the second current passing node of the second transistor, wherein the first terminal of the first fixed resistor is coupled to the first current passing node of the second transistor, wherein the control node of the second transistor is coupled to receive the second fixed voltage, and the second node of the second voltage generating source is coupled to the second terminal of the first fixed resistor, wherein the electronic circuit is operable to generate a second current signal at the second current passing node of the second transistor related to a resistance value of the first fixed resistor, wherein a current passing through the first load is equal to a difference between the first current signal and the second current signal.

### Claim 6 (depends on 5)

The electronic circuit of claim 5, wherein the first transistor is an NPN bipolar transistor and the second transistor is a bipolar PNP transistor

### Claim 7 (depends on 5)

The electronic circuit of claim 5, wherein the first transistor is a PNP bipolar transistor and the second transistor is an NPN bipolar transistor

### Claim 8 (depends on 5)

The electronic circuit of claim 5, wherein the first voltage generating source comprises a reference leg of a current mirror circuit.

### Claim 9 (depends on 5)

The electronic circuit of claim 5, further comprising:
a comparator coupled to the second current passing node of the first transistor for generating a two state output signal.

### Claim 10 (depends on 5)

The electronic circuit of claim 5, further comprising:
a second magnetoresistance element having first and second terminals;
a third transistor having a control node, and first current passing node, and a second current passing node;
a third voltage generating source having first and second nodes between which a third fixed voltage is generated, wherein the first terminal of the second magnetoresistance element is coupled to the first current passing node of the third transistor, wherein the control node of the third transistor is coupled to receive the third fixed voltage, and the second node of the third voltage generating source is coupled to the second terminal of the second magnetoresistance element, wherein the electronic circuit is operable to generate a third current signal at the second current passing node of the third transistor related to a resistance value of the second magnetoresistance element, wherein the electronic circuit further comprises:
a second fixed resistor having first and second terminals;
a fourth transistor having a control node, a first current passing node, and a second current passing node;
a fourth voltage generating source having first and second nodes between which a fourth fixed voltage is generated; and
a second load coupled to the second current passing node of the third transistor, wherein the second current passing node of the third transistor is coupled to the second current passing node of the fourth transistor, wherein the first terminal of the second fixed resistor is coupled to the first current passing node of the fourth transistor, wherein the control node of the fourth transistor is coupled to receive the fourth fixed voltage, and the second node of the fourth voltage generating source is coupled to the second terminal of the second fixed resistor, wherein the electronic circuit is operable to generate a fourth current signal at the second current passing node of the fourth transistor related to a resistance value of the second fixed resistor, wherein a current passing through the second load is equal to a difference between the third current signal and the fourth current signal.

### Claim 11 (depends on 10)

The electronic circuit of claim 10, wherein the first voltage generating source and the third voltage generating source are a same first common voltage generating source.

### Claim 12 (depends on 11)

The electronic circuit of claim 11, wherein the same first common voltage generating source comprises a reference leg of a current mirror circuit.

### Claim 13 (depends on 11)

The electronic circuit of claim 11, wherein the second voltage generating source and the fourth voltage generating source are a same second common voltage generating source.

### Claim 14 (depends on 13)

The electronic circuit of claim 13, wherein the same first common voltage generating source comprises a reference leg of a current mirror circuit and wherein the same second common voltage generating source comprises a common mode voltage detector circuit coupled to the first and second loads and configured to generate the first and third voltages as the same common mode voltage related to a common mode voltage between the first and second loads.

### Claim 15 (depends on 10)

The electronic circuit of claim 10, wherein the second voltage generating source and the fourth voltage generating source are a same common voltage generating source.

### Claim 16 (depends on 15)

The electronic circuit of claim 15, wherein the same common voltage generating source comprises a common mode voltage detector circuit coupled to the first and second loads and configured to generate the first and third voltages as the same common-mode-voltage related to a common mode voltage between the first and second loads.

### Claim 17 (depends on 1)

The electronic circuit of claim 1, further comprising:
a second magnetoresistance element having first and second terminals;
a second transistor having a control node, a first current passing node, and a second current passing node;
a second voltage generating source having first and second nodes between which a second fixed voltage is generated; and
a load coupled to the second current passing node of the first transistor, wherein the second current passing node of the first transistor is coupled to the second current passing node of the second transistor, wherein the first terminal of the second magnetoresistance element is coupled to the first current passing node of the second transistor, wherein the control node of the second transistor is coupled to receive the second fixed voltage, and the second node of the second voltage generating source is coupled to the second terminal of the second magnetoresistance element, wherein the electronic circuit is operable to generate a second current signal at the second current passing node of the second transistor related to a resistance value of the second magnetoresistance element, wherein a current passing through the load is equal to a difference between the first current signal and the second current signal, wherein the second terminals of the first and second magnetoresistance elements are not coupled together.

### Claim 18 (depends on 17)

The electronic circuit of claim 17, wherein the first voltage generating source comprises a reference leg of a current mirror circuit.

### Claim 19 (depends on 17)

The electronic circuit of claim 17, further comprising:
a comparator coupled to the second current passing node of the first transistor for generating a two state output signal.

### Claim 20 (depends on 17)

The electronic circuit of claim 17, further comprising:
a third magnetoresistance element having first and second terminals;
a third transistor having a control node, and first current passing node, and a second current passing node;
a third voltage generating source having first and second nodes between which a third fixed voltage is generated, wherein the first terminal of the third magnetoresistance element is coupled to the first current passing node of the third transistor, wherein the control node of the third transistor is coupled to receive the third fixed voltage, and the second node of the third voltage generating source is coupled to the second terminal of the third magnetoresistance element, wherein the electronic circuit is operable to generate a third current signal at the second current passing node of the third transistor related to a resistance value of the third magnetoresistance element, wherein the electronic circuit further comprises:
a fourth magnetoresistance element having first and second terminals;
a fourth transistor having a control node, a first current passing node, and a second current passing node;
a fourth voltage generating source having first and second nodes between which a fourth fixed voltage is generated; and
a second load coupled to the second current passing node of the third transistor, wherein the second current passing node of the third transistor is coupled to the second current passing node of the fourth transistor, wherein the first terminal of the fourth magnetoresistance element is coupled to the first current passing node of the fourth transistor, wherein the control node of the fourth transistor is coupled to receive the fourth fixed voltage, and the second node of the fourth voltage generating source is coupled to the second terminal of the fourth magnetoresistance element, wherein the electronic circuit is operable to generate a fourth current signal at the second current passing node of the fourth transistor related to a resistance value of the fourth magnetoresistance element, wherein a current passing through the second load is equal to a difference between the third current signal and the fourth current signal.

### Claim 21 (depends on 20)

The electronic circuit of claim 20, wherein the first voltage generating source and the third voltage generating source are a same first common voltage generating source.

### Claim 22 (depends on 21)

The electronic circuit of claim 21, wherein the same first common voltage generating source comprises a reference leg of a current mirror circuit.

### Claim 23 (depends on 21)

The electronic circuit of claim 21, wherein the second voltage generating source and the fourth voltage generating source are a same second common voltage generating source.

### Claim 24 (depends on 23)

The electronic circuit of claim 23, wherein the same first common voltage generating source comprises a reference leg of a current mirror circuit and wherein the same second common voltage generating source comprises a common mode voltage detector circuit coupled to the first and second loads and configured to generate the first and third voltages as the same common-mode voltage related to a common mode voltage between the first and second loads.

### Claim 25 (depends on 20)

The electronic circuit of claim 20, wherein the second voltage generating source and the fourth voltage generating source are a same common voltage generating source.

### Claim 26 (depends on 25)

The electronic circuit of claim 25, wherein the same common voltage generating source comprises a common mode voltage detector circuit coupled to the first and second loads and configured to generate the first and third voltages as the same common mode-related voltage related to a common mode voltage between the first and second loads.

### Claim 27

A magnetic field sensor coupled to receive a power supply voltage, comprising:
a substrate; and
an electronic circuit disposed upon the substrate, the electronic circuit comprising:
a first magnetoresistance element having first and second terminals;
a first transistor having a control node, a first current passing node, and a second current passing node; and
a first voltage generating source having first and second nodes between which a first fixed voltage is generated, wherein the first terminal of the first magnetoresistance element is coupled to the first current passing node of the first transistor, wherein the control node of the first transistor is coupled to receive the first fixed voltage, and the second node of the first voltage generating source is coupled to the second terminal of the first magnetoresistance element, wherein the electronic circuit is operable to generate a first current signal at the second current passing node of the first transistor related to a resistance value of the first magnetoresistance element, wherein the electronic circuit further comprises:
a second magnetoresistance element having first and second terminals;
a second transistor having a control node, a first current passing node, and a second current passing node;
a second voltage generating source having first and second nodes between which a second fixed voltage is generated; and
a load coupled to the second current passing node of the first transistor, wherein the second current passing node of the first transistor is coupled to the second current passing node of the second transistor, wherein the first terminal of the second magnetoresistance element is coupled to the first current passing node of the second transistor, wherein the control node of the second transistor is coupled to receive the second fixed voltage, and the second node of the second voltage generating source is coupled to the second terminal of the second magnetoresistance element, wherein the electronic circuit is operable to generate a second current signal at the second current passing node of the second transistor related to a resistance value of the second magnetoresistance element, wherein a current passing through the load is equal to a difference between the first current signal and the second current signal.

### Claim 28 (depends on 27)

The magnetic field sensor of claim 27, wherein the first voltage generating source comprises a reference leg of a current mirror circuit.

### Claim 29 (depends on 27)

The magnetic field sensor of claim 27, further comprising:
a comparator coupled to the second current passing node of the first transistor for generating a two state output signal.

### Claim 30

A magnetic field sensor coupled to receive a power supply voltage, comprising:
a substrate; and
an electronic circuit disposed upon the substrate, the electronic circuit comprising:
a first magnetoresistance element having first and second terminals;
a first transistor having a control node, and first current passing node, and a second current passing node;
a first voltage generating source having first and second nodes between which a first fixed voltage is generated, wherein the first terminal of the first magnetoresistance element is coupled to the first current passing node of the first transistor, wherein the control node of the first transistor is coupled to receive the first fixed voltage, and the second node of the first voltage generating source is coupled to the second terminal of the first magnetoresistance element, wherein the electronic circuit is operable to generate a first current signal at the second current passing node of the first transistor related to a resistance value of the first magnetoresistance element, wherein the electronic circuit further comprises:
a second magnetoresistance element having first and second terminals;
a second transistor having a control node, a first current passing node, and a second current passing node; and
a second voltage generating source having first and second nodes between which a second fixed voltage is generated;
a load coupled to the second current passing node of the first transistor, wherein the second current passing node of the first transistor is coupled to the second current passing node of the second transistor, wherein the first terminal of the second magnetoresistance element is coupled to the first current passing node of the second transistor, wherein the control node of the second transistor is coupled to receive the second fixed voltage, and the second node of the second voltage generating source is coupled to the second terminal of the second magnetoresistance element, wherein the electronic circuit is operable to generate a second current signal at the second current passing node of the second transistor related to a resistance value of the second magnetoresistance element, wherein a current passing through the load is equal to a difference between the first current signal and the second current signal, wherein the electronic circuit further comprises:
a third magnetoresistance element having first and second terminals;
a third transistor having a control node, and first current passing node, and a second current passing node; and
a third voltage generating source having first and second nodes between which a third fixed voltage is generated, wherein the first terminal of the third magnetoresistance element is coupled to the first current passing node of the third transistor, wherein the control node of the third transistor is coupled to receive the third fixed voltage, and the second node of the third voltage generating source is coupled to the second terminal of the third magnetoresistance element, wherein the electronic circuit is operable to generate a third current signal at the second current passing node of the third transistor related to a resistance value of the third magnetoresistance element, wherein the electronic circuit further comprises:
a fourth magnetoresistance element having first and second terminals;
a fourth transistor having a control node, a first current passing node, and a second current passing node;
a fourth voltage generating source having first and second nodes between which a fourth fixed voltage is generated; and
a second load coupled to the second current passing node of the third transistor, wherein the second current passing node of the third transistor is coupled to the second current passing node of the fourth transistor, wherein the first terminal of the fourth magnetoresistance element is coupled to the first current passing node of the fourth transistor, wherein the control node of the fourth transistor is coupled to receive the fourth fixed voltage, and the second node of the fourth voltage generating source is coupled to the second terminal of the fourth magnetoresistance element, wherein the electronic circuit is operable to generate a fourth current signal at the second current passing node of the fourth transistor related to a resistance value of the fourth magnetoresistance element, wherein a current passing through the second load is equal to a difference between the third current signal and the fourth current signal.

### Claim 31 (depends on 30)

The magnetic field sensor of claim 30, wherein the first voltage generating source and the third voltage generating source are a same first common voltage generating source.

### Claim 32 (depends on 31)

The magnetic field sensor of claim 31, wherein the same first common voltage generating source comprises a reference leg of a current mirror circuit.

### Claim 33 (depends on 31)

The magnetic field sensor of claim 31, wherein the second voltage generating source and the fourth voltage generating source are a same second common voltage generating source.

### Claim 34 (depends on 33)

The magnetic field sensor of claim 33, wherein the same first common voltage generating source comprises a reference leg of a current mirror circuit and wherein the same second common voltage generating source comprises a common mode voltage detector circuit coupled to the first and second loads and configured to generate the first and third voltages as the same common-mode voltage related to a common mode voltage between the first and second loads.

### Claim 35 (depends on 30)

The magnetic field sensor of claim 30, wherein the second voltage generating source and the fourth voltage generating source are a same common voltage generating source.

### Claim 36 (depends on 35)

The magnetic field sensor of claim 35, wherein the same common voltage generating source comprises a common mode voltage detector circuit coupled to the first and second loads and configured to generate the first and third voltages as the same common-mode voltage related to a common mode voltage between the first and second loads.

### Claim 37 (depends on 30)

The magnetic field sensor of claim 30, wherein the electronic circuit further comprises:
a fifth magnetoresistance element having first and second terminals;
a fifth transistor having a control node, and first current passing node, and a second current passing node;
a fifth voltage generating source having first and second nodes between which a fifth fixed voltage is generated, wherein the first terminal of the fifth magnetoresistance element is coupled to the first current passing node of the fifth transistor, wherein the control node of the fifth transistor is coupled to receive the fifth fixed voltage, and the second node of the fifth voltage generating source is coupled to the second terminal of the fifth magnetoresistance element, wherein the electronic circuit is operable to generate a first current signal at the second current passing node of the fifth transistor related to a resistance value of the fifth magnetoresistance element, wherein the electronic circuit further comprises:
a sixth magnetoresistance element having first and second terminals;
a sixth transistor having a control node, an first current passing node, and a second current passing node; and
a sixth voltage generating source having first and second nodes between which a sixth fixed voltage is generated;
a load coupled to the second current passing node of the fifth transistor, wherein the second current passing node of the fifth transistor is coupled to the second current passing node of the sixth transistor, wherein the first terminal of the sixth magnetoresistance element is coupled to the first current passing node of the sixth transistor, wherein the control node of the sixth transistor is coupled to receive the sixth fixed voltage, and the second node of the sixth voltage generating source is coupled to the second terminal of the sixth magnetoresistance element, wherein the electronic circuit is operable to generate a second current signal at the second current passing node of the sixth transistor related to a resistance value of the sixth magnetoresistance element, wherein a current passing through the load is equal to a difference between the first current signal and the second current signal, wherein the electronic circuit further comprises:
a seventh magnetoresistance element having first and second terminals;
a seventh transistor having a control node, and first current passing node, and a second current passing node; and
a seventh voltage generating source having first and second nodes between which a seventh fixed voltage is generated, wherein the first terminal of the seventh magnetoresistance element is coupled to the first current passing node of the seventh transistor, wherein the control node of the seventh transistor is coupled to receive the seventh fixed voltage, and the second node of the seventh voltage generating source is coupled to the second terminal of the seventh magnetoresistance element, wherein the electronic circuit is operable to generate a third current signal at the second current passing node of the seventh transistor related to a resistance value of the seventh magnetoresistance element, wherein the electronic circuit further comprises:
an eighth magnetoresistance element having first and second terminals;
an eighth transistor having a control node, a first current passing node, and a second current passing node;
an eighth voltage generating source having first and second nodes between which an eighth fixed voltage is generated; and
a second load coupled to the second current passing node of the seventh transistor, wherein the second current passing node of the seventh transistor is coupled to the second current passing node of the eighth transistor, wherein the first terminal of the eighth magnetoresistance element is coupled to the first current passing node of the eighth transistor, wherein the control node of the eighth transistor is coupled to receive the eighth fixed voltage, and the second node of the eighth voltage generating source is coupled to the second terminal of the eighth magnetoresistance element, wherein the electronic circuit is operable to generate a fourth current signal at the second current passing node of the eighth transistor related to a resistance value of the eighth magnetoresistance element, wherein a current passing through the second load is equal to a difference between the third current signal and the fourth current signal.

### Claim 38 (depends on 37)

The magnetic field sensor of claim 37, wherein the first voltage generating source, the third voltage generating source, the fifth voltage generating source, and the seventh voltage generating source are a same first common voltage generating source, the second voltage generating source and the fourth voltage generating source are a same second common voltage generating source, and the sixth voltage generating source and the eighth voltage generating source are a same third common voltage generating source.