JPH06201806A - Magnetic sensor device - Google Patents

Abstract

PURPOSE:To prevent the fluctuation in amplification degree due to the unevenness of characteristics of a magnetoresistance element and the differences of temperature-resistance characteristics. CONSTITUTION:Magnetoresistance elements M1, M2 are connected in series and the series circuit is connected to Vcc-Gnd terminals of a power source. After the voltage Va of the connection point of the magnetoresistance elements M1, M2 is buffered and amplified by a buffer B, the voltage is amplified by a reversal amplifier A1. The output of the reversal amplifier A1 is regarded as a detection voltage Vo. As a result, even when there are the unevenness of characteristics of the magnetoresistance elements and the differences of temperature-resistance characteristics, the fluctuation of amplification degree does not occur. Further, it is unnecessary to make the characteristics of the magnetoresistance elements uniform, thereby improving the manufacturing yield of the title devices.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic sensor device, and more particularly to a magnetic sensor device which eliminates inconveniences due to variations in the characteristics of magnetoresistive elements and differences in temperature-resistance characteristics.

[0002]

2. Description of the Related Art FIG. 5 is a circuit diagram showing an example of a conventional magnetic sensor device used in a bill validator. In this magnetic sensor device 51, the magnetic resistance element M is provided in the vicinity of the bill insertion slit in the socket S in parallel with the moving direction of the bill M.
1, M2 are installed internally. The magnetoresistive elements M1 and M2 are connected in series, and the series circuit is connected between the power supply Vcc and Gnd. Then, the voltage Va at the connection point between the magnetoresistive elements M1 and M2 is input to the inverting input terminal of the inverting amplifier A1 via the capacitor C and the input resistor Ri. A feedback resistor Rf is connected between the inverting input terminal and the output terminal of the inverting amplifier A1, and the reference voltage Vr is input to the non-inverting input terminal of the inverting amplifier A1. Then, the detection voltage Vo is output from the output terminal of the inverting amplifier A1.

Next, the operation of the magnetic sensor device 51 will be described. When a bill is inserted, the voltage Va of the voltage Va at the connection point has the waveform shown in (a) of FIG. However, Vi shows a neutral voltage. The detection voltage Vo output from the inverting amplifier A1 is Vo = [− Rf / {Ri + M1 · M2 / (M1 + M2)}] · k · Vcc (1), and thus has the waveform shown in (b) of FIG. .

[0004]

In the conventional magnetic sensor device 51 described above, the inverting amplifier A is used as can be seen from the equation (1).
Since the amplification factor of 1 depends on the magnetoresistive elements M1 and M2,
Even if the input resistance Ri and the feedback resistance Rf are made equal, there is a problem in that the amplification degree varies due to variations in the magnetoresistive elements M1 and M2 and temperature-resistance characteristics. Further, if the characteristics of the magnetoresistive elements M1 and M2 are made uniform in order to eliminate the variation in the amplification degree, there is a problem that the yield is reduced. Therefore, an object of the present invention is to provide a magnetic sensor device in which the detection voltage does not fluctuate even if there are variations in the characteristics of the magnetoresistive elements or differences in temperature-resistance characteristics, and to improve the yield.

[0005]

In the magnetic sensor device according to the present invention, a magnetic sensor consisting of two magnetoresistive elements connected in series is connected between a power source Vcc and Gnd, and the connection point of the two magnetoresistive elements is connected. A signal voltage is taken out from the device, and the signal voltage is inputted to an amplifier via a buffer, or is inputted to an amplifier having a high input impedance with respect to the magnetic sensor, and the output of the amplifier is taken out as a detection signal. It is a feature.

[0006]

In the magnetic sensor device according to the present invention, the signal voltage from the connection point of the two magnetoresistive elements is input to the amplifier via the buffer, or an amplifier having a high input impedance is used for the magnetic sensor. Therefore, variations in the characteristics of the magnetoresistive element and differences in temperature-resistance characteristics do not affect the amplification degree of the amplifier. In addition, the magnetic resistance element M
Since it is not necessary to match the characteristics of 1 and M2, the yield is improved.

[0007]

The present invention will be described in more detail with reference to the embodiments shown in the drawings. The present invention is not limited to this.

First Embodiment FIG. 1 shows a magnetic sensor device according to a first embodiment of the present invention, which is used in a bill validator. In this magnetic sensor device 1, in the vicinity of the bill insertion slit in the socket S, the magnetic resistance elements M1 and M are arranged parallel to the moving direction of the bill M.
2 is installed internally. The magnetoresistive elements M1 and M2 are connected in series, and the series circuit is connected between the power supply Vcc and Gnd. Then, the voltage Va at the connection point between the magnetoresistive elements M1 and M2 is input to the buffer B. Its buffer B
Output voltage Vb is input to the inverting input terminal of the inverting amplifier A1 via the capacitor C and the input resistor Ri. A feedback resistor Rf is connected between the inverting input terminal and the output terminal of the inverting amplifier A1, and the reference voltage Vr is input to the non-inverting input terminal of the inverting amplifier A1. Then, the detection voltage Vo is output from the output terminal of the inverting amplifier A1.

Next, the operation of the magnetic sensor device 1 will be described. When a bill is inserted, the voltage Va of the connection point voltage Va has a waveform shown in FIG. However, Vi shows a neutral voltage. Therefore, the output voltage Vb from the buffer B
Has the waveform shown in FIG. The detection voltage Vo output from the inverting amplifier A1 is Vo = (− Rf / Ri) · Vb (2), and thus has the waveform shown in (c) of FIG.

As can be seen from the equation (2), the amplification degree of the inverting amplifier A1 depends only on the input resistance Ri and the feedback resistance Rf, and does not depend on the magnetoresistive elements M1 and M2. That is, the amplification degree is not affected by variations in the magnetoresistive elements M1 and M2 and differences in temperature characteristics. Therefore, the magnetoresistive element M
It is not necessary to match the characteristics of 1 and M2, and the yield can be improved.

-Second Embodiment- FIG. 3 shows a magnetic sensor device according to a second embodiment of the present invention, which is used in a bill validator. In this magnetic sensor device 21, in the vicinity of the bill insertion slit in the socket S, the magnetic resistance elements M1 and M1 are arranged parallel to the moving direction of the bill M.
M2 is installed internally. The magnetoresistive elements M1 and M2 are connected in series, and the series circuit is connected between the power supply Vcc and Gnd. The voltage Vp at the connection point between the magnetoresistive elements M1 and M2 is input to the non-inverting input terminal of the non-inverting amplifier A2. A feedback resistor Rb is connected between the inverting input terminal and the output terminal of the non-inverting amplifier A2, and the inverting input terminal of the non-inverting amplifier A2 is grounded via a grounding resistor Ra and a grounding capacitor C1. The output voltage Vq of the non-inverting amplifier A2 is input via the capacitor C2 to the voltage dividing point adjusted to the reference voltage Vr by the resistors R1 and R2, and the voltage at the voltage dividing point is used as the detection voltage Vo. Is output.

Next, the operation of the magnetic sensor device 21 will be described. When a bill is inserted, the voltage Vp of the voltage Va at the connection point has the waveform shown in FIG. However, Vi shows a neutral voltage. Therefore, the output voltage Vq from the non-inverting amplifier A2 has the waveform shown in FIG. Since the detected voltage Vo is Vo = (1 + Rb / Ra) · Vp (3), it has the waveform shown in FIG. 4 (c).

As can be seen from the equation (2), the non-inverting amplifier A2
The amplification degree of depends only on the feedback resistance Rb and the ground resistance Ra,
It does not depend on the magnetoresistive elements M1 and M2. That is, the amplification degree is not affected by variations in the magnetoresistive elements M1 and M2 and differences in temperature characteristics. Therefore, the magnetoresistive element M
It is not necessary to match the characteristics of 1 and M2, and the yield can be improved.

[0014]

According to the magnetic sensor device of the present invention, the amplification factor does not change even if there is a variation in the characteristics of the magnetoresistive element or a difference in temperature-resistance characteristics. And for this reason,
It is not necessary to match the characteristics of the magnetoresistive elements, and the yield can be improved.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a first embodiment of a magnetic sensor device of the present invention.

FIG. 2 is a waveform diagram of each part of the magnetic sensor device of FIG.

FIG. 3 is a circuit diagram showing a second embodiment of the magnetic sensor device of the present invention.

FIG. 4 is a waveform diagram of each part of the magnetic sensor device of FIG.

FIG. 5 is a circuit diagram showing an example of a conventional magnetic sensor device.

6 is a waveform diagram of each part of the magnetic sensor device of FIG.

[Explanation of symbols]

 1 magnetic sensor device 21 magnetic sensor device 51 magnetic sensor device M1 magnetic resistance element M2 magnetic resistance element A1 inverting amplifier A2 non-inverting amplifier C capacitor C1 grounding capacitor C2 capacitor Ra grounding resistance Rb feedback resistance Rf feedback resistance Ri input resistance R1 resistance R2 resistance Vo detection voltage

Claims (1)

[Claims] 1. A magnetic sensor comprising two magnetoresistive elements connected in series is connected between a power supply Vcc and Gnd, a signal voltage is taken out from a connection point of the two magnetoresistive elements, and the signal voltage is buffered. A magnetic sensor device, characterized in that it is inputted to an amplifier via an amplifier or is inputted to an amplifier having a high input impedance with respect to the magnetic sensor, and an output of the amplifier is taken out as a detection signal.