US 5,402,064 A · Magnetoresistive sensor circuit with high output voltage swing and temperature compensation

Abstract

A magnetoresistor (MR) and a non-magnetoresistor (NMR) are formed of indium antimonide or other magnetoresistive material in thermal proximity to each other on an integrated circuit substrate (100). Hall effect shorting strips (104) are formed on the magnetoresistor (MR) to make it much more magnetoresistive than the non-magnetoresistor (NMR). A current mirror (80) causes equal constant currents (I2) which do not vary with temperature to flow through the magnetoresistor (MR) and non-magnetoresistor (NMR), such that magnetoresistor and non-magnetoresistor voltages are developed thereacross respectively. The magnetoresistor and non-magnetoresistor voltages vary equally in accordance with temperature. The magnetoresistor voltage also varies in accordance with applied magnetic flux. A comparator (66) subtracts the non-magnetoresistor voltage from the magnetoresistor voltage to produce an output signal (Vout) with the temperature variation canceled, and which thereby varies only in accordance with magnetic flux. The current mirror (80) has an essentially infinite equivalent load impedance, such that the magnetoresistor voltage varies to a maximum possible extent with variation of the resistance of the magnetoresistor (MR) and the sensor (70) has a maximum possible output voltage swing.

Claims18

Dependent claims

A magnetoresistive sensor circuit, comprising:

a magnetoresistor having a resistance which varies with an applied magnetic flux;
a non-magnetoresistor which is disposed in thermal proximity to the magnetoresistor and has a resistance which is substantially unaffected by said magnetic flux;
said resistances of the magnetoresistor and non-magnetoresistor varying substantially identically with temperature;
a non-resistive constant current source means for causing substantially equal and constant currents to flow through the magnetoresistor and non-magnetoresistor to develop mangetoresistor and non-magnetoresistor voltages thereacross respectively;
and
computing means for producing an output signal as a predetermined function of said magnetoresistor and non-magnetoresistor voltages.

3 more elements

A magnetoresistive sensor circuit, comprising:

a magnetoresistor having a resistance which varies with an applied magnetic flux;
a non-magnetoresistor which is disposed in thermal proximity to the magnetoresistor and has a resistance which is substantially unaffected by said magnetic flux;
said resistances of the magnetoresistor and non-magnetoresistor varying substantially identically with temperature;
constant current source means for causing substantially equal and constant currents to flow through the magnetoresistor and non-magnetoresistor to develop mangetoresistor and non-magnetoresistor voltages thereacross respectively in which the constant current source means comprises:
voltage source means;
a first transistor having a first controlled current path connected in series with the magnetoresistor across the voltage source means, and a first current control terminal;
a second transistor having a second controlled current path connected in series with the non-magnetoresistor across the voltage source means, and a second current control terminal;
and
reference voltage source means for applying a predetermined reference voltage to said first and second current control terminals;
and
computing means for producing an output signal as a predetermined function of said magnetoresistor and non-magnetoresistor voltages.

8 more elements

A magnetoresistive integrated circuit sensor, comprising;

a substrate;
a magnetoresistor which is formed on the substrate and has a resistance which varies with temperature and also with an applied magnetic flux;
a non-magnetoresistor which is formed on the substrate in thermal proximity to the magnetoresistor and has a resistance which varies with temperature and is substantially unaffected by said magnetic flux;
constant current source means for causing constant currents to flow through the magnetoresistor and non-magnetoresistor to develop magnetoresistor an non-magnetoresistor voltages thereacross respectively which vary substantially equally with temperature in which the constant current source means comprises:
voltage source means;
a first transistor which is formed on the substrate and has a controlled current path connected in series with the magnetoresistor across the voltage source means, and a first current control terminal;
a second transistor which is formed on the substrate and has a controlled current path connected in series with the non-magnetoresistor across the voltage source means, and a second current control terminal;
and
reference voltage source means for applying a predetermined reference voltage to said first and second current control terminals;
and
computing means for producing an output signal as a predetermined function of said magnetoresistor and non-magnetoresistor voltages.

8 more elements

Dependencies are inferred from the claim text.

Magnetoresistive sensor circuit with high output voltage swing and temperature compensation

Life of this patent

Magnetoresistive sensor circuit with high output voltage swing and temperature compensation

Life of this patent

Abstract

Claims18