JPH03183976A - Magnetic sensor - Google Patents

Abstract

PURPOSE:To improve the temperature characteristic of the sensitivity and to prevent the sensitivity from decreasing as temperature rises by forming magneto- resistance effect elements of ferromagnetic alloy thin film constitution on a silicon substrate and supplying a constant to the element. CONSTITUTION:This sensor is constituted by composing a constant-current circuit 4 of the magneto-resistance effect elements 2 and 3, an FET (field effect transistor), a resistance 6, etc., on the silicon substrate 1. This sensor is fitted to a motor, etc., and a source voltage is applied between a power source and ground terminals 7 and 9 to supply constant currents to the elements 2 and 3. Consequently, the motor rotates and then a magnetic field operates in the surface of the substrate 1 to saturate the elements 2 and 3 magnetically. Then a voltage which varies with the direction of the magnetic field is developed between an output terminal 8 and the terminal 9. Even if the ambient temperature varies in this state, the constant currents flow to the elements 2 and 3, so the temperature characteristics of the sensitivity of the sensor is good and the sensitivity never deteriorates.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to a magnetic sensor used for position detection, rotational speed control, etc. of a motor or the like.

``Prior art'' Among conventional magnetic sensors, those that utilize the magnetoresistive effect of ferromagnetic metals are made of nickel-iron (Ni-Fe) or cobalt-iron (Co-F) by vacuum deposition on a glass substrate.
After forming a ferromagnetic metal alloy thin film such as e), a predetermined pattern is formed by a photolithography process or the like.

``Problem to be solved by the invention-1 By the way, in the conventional magnetic sensor mentioned above, the temperature characteristic of sensitivity is poor (approximately -4,000 ppm/℃), and as the ambient temperature rises, the sensitivity as a magnetic sensor decreases. The disadvantage was that it decreased.

Therefore, there is a problem that position detection and rotational speed control of the motor etc. cannot be performed accurately in a place where temperature changes are large.

The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to provide a magnetic sensor with improved temperature characteristics of sensitivity and whose sensitivity does not decrease even when the ambient temperature rises.

"Means for Solving the Problems" A magnetic sensor according to the present invention includes a magnetoresistive element formed of a ferromagnetic alloy thin film on a silicon substrate, and a constant current applied to the magnetoresistive element on the silicon substrate. It is characterized by forming a constant current circuit that supplies .

"Operation" According to the present invention, even if the ambient temperature changes, a constant current flows through the magnetoresistive element, so the temperature characteristic of the sensitivity of this magnetic sensor is good and the sensitivity does not deteriorate.

"Embodiment" Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a perspective view showing the configuration of a magnetic sensor according to an embodiment of the present invention, and FIG. 2 is a circuit diagram of FIG. Silicon produced by Bridgman method etc. (
Si) - A silicon substrate cut out from a bulk single crystal; 2 and 3 are respectively magnetoresistive elements made of ferromagnetic alloy thin films such as nickel-iron (Ni-Fe) or cobalt-iron (Co-Fe); It is formed on the substrate l by vacuum evaporation or the like, and is formed into a predetermined pattern by a photolithography process or the like.

Further, 4 is a constant current circuit formed on the silicon substrate 1 by an impurity diffusion method, a photolithography process, etc., and is composed of an FET (field effect transistor) 5, a resistor 6, and the like. 7 is a power supply terminal to which the power supply voltage VDD is applied, 8 is an output terminal, 9 is a ground terminal, 1
0 to 13 are conductor patterns that electrically connect the circuit elements 2 to 4 and the terminals 7 to 9.

In such a configuration, first, this magnetic sensor is attached to a motor or the like, and a power supply voltage Vno is applied between the power supply terminal 7 and the ground terminal 9 to cause a constant current fc to flow through the magnetoresistive elements 2 and 3.

As a result, when a motor or the like rotates and a magnetic field sufficient to saturate the magnetization of the magnetoresistive elements 2 and 3 acts within the plane of the silicon substrate I, a gap between the output terminal 8 and the ground terminal 9 is generated. A voltage V(θ) is generated that changes depending on the angle θ between the current and magnetization, that is, the direction of the magnetic field.

In this state, even if the ambient temperature of this magnetic sensor changes, a constant current iC flows through the magnetoresistive elements 2 and 3, so the temperature characteristics of the sensitivity of this magnetic sensor are good, and the sensitivity is poor. It won't happen.

As explained above, the magnetoresistive element is formed on a silicon substrate, and a constant current circuit is formed on the same substrate to flow a constant current through the magnetoresistive element, so the temperature characteristics of the sensitivity are good. (-500 ppm/℃), which can suppress the decrease in sensitivity of the magnetic sensor caused by an increase in ambient temperature.

Here, FIG. 3 shows the temperature characteristics of sensitivity of a magnetic sensor according to an embodiment of the present invention and a conventional magnetic sensor.

In this figure, curve a is the temperature characteristic of sensitivity of the magnetic sensor according to an embodiment of the present invention, and curve a is the temperature characteristic of sensitivity of the conventional magnetic sensor. As can be seen from this figure, the temperature characteristics are significantly improved compared to conventional magnetic sensors.

"Effects of the Invention" As explained above, according to the present invention, a magnetoresistive element made of a ferromagnetic alloy thin film is formed on a silicon substrate, and the magnetoresistive element is formed on the silicon substrate. Since a constant current circuit that supplies a constant current is formed, there is an effect that the temperature characteristics of sensitivity are good.

This has the effect that sensitivity does not decrease even if the ambient temperature increases.

Therefore, there is an effect that the position detection and rotational speed control of the motor etc. can be performed accurately.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing the configuration of a magnetic sensor according to an embodiment of the present invention, FIG. 2 is a circuit diagram of FIG. 1, and FIG. 3 is a diagram of a magnetic sensor according to an embodiment of the present invention and a conventional magnetic sensor. FIG. 3 is a diagram showing the temperature dependence of the sensitivity. ! ... Silicon substrate, 2.3 ... Magnetoresistive element, 4 ... Constant current circuit, 5 ... F
ET16...Resistance.

Claims (1)

[Claims] A magnetic sensor characterized in that a magnetoresistive element made of a ferromagnetic alloy thin film is formed on a silicon substrate, and a constant current circuit that supplies a constant current to the magnetoresistive element is formed on the silicon substrate. .