Magnetic field sensor and electronic circuit that pass amplifier current through a magnetoresistance element

Patent metadata

Field	Value
Publication number	US-10712403-B2
Application number	US-201715624898-A
Country	US
Kind code	B2
Filing date	Jun 16, 2017
Priority date	Oct 31, 2014
Publication date	Jul 14, 2020
Grant date	Jul 14, 2020

Abstract

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

First claim

What is claimed is:

1. An electronic circuit coupled to receive a power supply voltage, comprising:
a first magnetoresistance element having first and second terminals, each one of the first and second terminals directly coupled to the magnetoresistance element;
a first transistor having a control node, a first current passing node, and a second current passing node;
a first fixed voltage generating source having first and second nodes between which a first fixed voltage is generated, wherein the first fixed voltage does not change in response to a changing magnetic field, 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 receives the first fixed voltage, and the second node of the first fixed 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;
a first fixed resistor having a first fixed resistance that does not change in response to the changing magnetic field and 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 fixed voltage generating source having first and second nodes between which a second fixed voltage is generated, wherein the second fixed voltage does not change in response to the changing magnetic field; 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 receives the second fixed voltage, and the second node of the second fixed 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.

2. The electronic circuit of claim 1 , wherein the first transistor is an NPN bipolar transistor and the second transistor is a bipolar PNP transistor.

3. The electronic circuit of claim 1 , wherein the first transistor is a PNP bipolar transistor and the second transistor is an NPN bipolar transistor.

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

5. 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.

6. The electronic circuit of claim 1 , 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 fixed voltage generating source having first and second nodes between which a third fixed voltage is generated, wherein the third fixed voltage does not change in response to the changing magnetic field, 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 receives the third fixed voltage, and the second node of the third fixed 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 a second fixed resistance that does not change in response to a changing magnetic field and 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 fixed voltage generating source having first and second nodes between which a fourth fixed voltage is generated, wherein the fourth fixed voltage does not change in response to the changing magnetic field; 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 receives the fourth fixed voltage, and the second node of the fourth fixed 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.

7. The electronic circuit of claim 6 , wherein the first fixed voltage generating source and the third fixed voltage generating source are a same first common fixed voltage generating source.

8. The electronic circuit of claim 7 , wherein the same first common fixed voltage generating source comprises a reference leg of a current mirror circuit.

9. The electronic circuit of claim 7 , wherein the second fixed voltage generating source and the fourth fixed voltage generating source are a same second common fixed voltage generating source.

10. The electronic circuit of claim 9 , wherein the same first common fixed voltage generating source comprises a reference leg of a current mirror circuit and wherein the same second common fixed 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 fixed voltages as the same common mode voltage related to a common mode voltage between the first and second loads.

11. The electronic circuit of claim 6 , wherein the second fixed voltage generating source and the fourth fixed voltage generating source are a same common fixed voltage generating source.

12. The electronic circuit of claim 11 , wherein the same common fixed 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 fixed voltages as the same common mode voltage related to a common mode voltage between the first and second loads.

13. An electronic circuit coupled to receive a power supply voltage, comprising:
a first magnetoresistance element having first and second terminals, each one of the first and second terminals directly coupled to the magnetoresistance element;
a first transistor having a control node, a first current passing node, and a second current passing node;
a first fixed voltage generating source having first and second nodes between which a first fixed voltage is generated, wherein the first fixed voltage does not change in response to a changi

Assignees

• Allegro Microsystems Llc

Inventors

• Drouin Mathew
• Fernandez Devon
• Towne Jay M
• Milesi Alejandro Gabriel

Classifications

• G01R33/0023

  Electronic aspects, e.g. circuits for stimulation, evaluation, control; Treating the measured signals; calibration (G01R33/0017 takes precedence) · CPC title

• G01R33/028

  Electrodynamic magnetometers · CPC title

• G01R33/09 Primary

  Magnetoresistive devices · CPC title