JPH0384484A - Magnetic sensor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] The present invention relates to a magnetic sensor, and more specifically, to a magnetic sensor, and more particularly, to a magnetic tape read head of a VTR or player, a brushless DD motor control, or an angle of a rotating part of precision equipment. This invention relates to a high-precision magnetic sensor using the Hall effect used for detection.

Hall elements using strained GaAs semiconductors can distinguish between north and south poles and provide a signal proportional to magnetic flux density, so they can be used to detect angles of rotation control parts in control equipment and automobiles. A magnetic sensor including a large number of Hall elements 11 as shown in FIG. 6 is used for detection or control of a Hall motor.

This magnetic sensor uses electrically semi-insulating 1-GaA
A cross-shaped n-GaAs layer is formed by selectively implanting ions into the s substrate 10, and each Hall element (rl-GaAs layer) 11 is constructed using this n-GaAs layer.

Such a magnetic sensor has four terminals 11n, Ita, Vtn, Vzrt (n=1 to
3), and two sets of terminals corresponding to each other.1. ．． ,
Engineering 2. ．． is used as a current terminal, or Vrn*Van is used as a Hall terminal, that is, as a terminal for current supply or Hall voltage measurement. For example, when a constant current is applied between the current terminals Iln and Inn of each Hall element, a voltage proportional to the magnetic flux density B of the magnetic field applied to this element is generated between the Hall terminals V1 and V2n. do.

This voltage is then detected by a dedicated voltmeter for each. Therefore, each terminal is connected to a bonding bat 12 for connecting an external constant current supply source or a Hall voltage measuring instrument, and a large number of bonding bats 12 are formed on the 1-GaAs substrate 10. has been done.

In the conventional magnetic sensor as described above, each Hall element 11 has four terminals, and it is necessary to connect the bonding bat 12 to each of these terminals. , Therefore, a large number of bonding bats 1 are placed on the substrate 10.
2 needs to be installed. Moreover, the bonding bat 12 requires an area of at least about 50 μm or more,
Furthermore, because the spacing between the bonding butts 12 cannot be narrowed to less than about 50 LLm, conventional magnetic sensors have a limitation in the density (arrangement pitch) of each Hall element 11, and have had the problem of not being able to detect a highly accurate magnetic field distribution. .

The present invention was made in view of these problems, and
By sequentially and selectively operating the Hall elements arranged in high density in a time-series manner, the number of bonding butts can be reduced, the Hall elements can be arranged in high density on the substrate, and the magnetic field distribution can be detected with high precision. Moreover, it is an object of the present invention to provide a magnetic sensor that is miniaturized.

In order to achieve the above object, the magnetic sensor according to the present invention has the following features:
In a magnetic sensor in which two or more Hall elements are arranged on a substrate, a switch is connected to at least one of the current terminals of the side Hall elements, and each Hall terminal is connected to a detection line through a capacitor. It is characterized by being connected to.

For example, to explain in more detail based on the circuit diagram of FIG. 5, a DC current B16 is interposed between the current terminals 11 and 2 of the Hall element 11 via a switch 15, and the Hall terminals vl and V2 are connected to each other. An external detection circuit 21 is connected by a detection line 19.20 via a capacitor 17.18.

Here, when the switch 15 disposed between the current terminals I- and Ii of the Hall element 11 is closed and a constant current is passed from the DC power supply 16, the Hall element 11 becomes in an operating state, and the current is applied to the Hall element 11. The voltage fluctuation corresponding to the magnetic flux density of the magnetic field, the so-called Hall voltage, is at the Hall terminals V, , V
, induced between. This induced Hall terminal V l,
Voltage fluctuations between Vs and Vs are converted by capacitors 17.18 connected to the Hall terminals V, , V into displacement currents flowing through the capacitors. This converted displacement current then passes through the detection lines 19 and 20 to the external detection circuit 2.
1, and the strength of the magnetic field applied to the Hall element 11 is detected.

The external detection circuit 21 uses operational amplifiers 24 and 25 having high input impedance and feedback impedance of capacitors 22 and 23, and an amplifier 26 at the final output stage. In other words, when the magnetic flux density changes and voltage fluctuations of Δv8 and Δv2 occur in the voltages of the Hall terminals V, V, respectively, displacement currents of Δv8 and Δv2 flow through the capacitors 17 and 18 at this time. . In this case, voltage fluctuations ΔV3, Δv2 and displacement current ΔI
1%Δ■, and the capacitance of capacitor 17.18 is C.
3, Δ11=C1Δv11Δ1. There is a relationship of =C, Δ■2.

This displacement current is integrated by a capacitor 22.23 which is a feedback impedance connected to the output side and input side (- side) of the operational amplifier 24.25, and the output vm and vA of each operational amplifier 24.25 are expressed as
If the capacitance of capacitor 22.23 is C1, Vi = - (CI / Cm ) Δ■2, Va = (
CI /Cm ) ΔV+ occurs. This difference VA-V,
If we take , the detection output V out is v,,, = (CI /C*) (Δv, -ΔV+) =
(c, /C*) ΔV, and an output proportional to the Hall voltage ΔV between the Hall terminals V+ and Vi can be detected.

According to the above means, a switch is connected to at least one of the current terminals of two or more Hall elements arranged on the substrate. Therefore, when the above-mentioned Hall elements are selectively turned on by activating the switches individually or sequentially, the Hall terminals of the individual Hall elements in the operating state will have the same effect as described in detail in the section. A Hall voltage proportional to the magnetic flux density due to the magnetic field applied to the Hall element is sequentially generated, and when the magnetic flux density changes, the Hall voltage also changes in accordance with the change in the magnetic flux density.

The voltage fluctuation generated at the Hall terminal is converted into a displacement current flowing through the capacitor, and this converted displacement current flows through the detection line and is detected by an externally provided operational amplifier or the like.

Therefore, the detection line connected to the Hall terminal via the capacitor can be shared, and the number of bonding bats can be reduced. Moreover, it becomes possible to increase the arrangement density of Hall elements by an amount corresponding to the reduction in bonding butts, and it becomes possible to detect the magnetic flux density distribution with high precision. Furthermore, it becomes possible to downsize the magnetic sensor itself.

Embodiments of the magnetic sensor according to the present invention will be described below with reference to the drawings. Note that components having the same functions as those of the conventional example are given the same reference numerals.

FIG. 1 shows an embodiment of a magnetic sensor according to the present invention, in which a Hall element 11 according to the present embodiment is made of n-GaA
s (carrier concentration I x 10"Cm-') layer 31,
It is formed into a cross shape by selectively etching it using photolithography. n-GaAs layer 3
As shown in FIG. 2, an insulating layer 32 made of a high-resistance i-GaAs layer or a CaF2 layer is provided between the Si substrate 1 and the Si substrate 30. Further, as shown in FIG. 1, a shift register 33i3 and a switching transistor 15 made of MO3 type transistors are formed on the Si substrate 30, and these switching transistors 15 serve as current terminals for the Hall element 11. and DC power supply 16
The shift register 33 is interposed between the shift register 33 and the shift register 33, and is turned on or off by the control signal of the shift register 33. On the other hand, the current terminal. is connected to the ground wire 35.

Furthermore, as shown in FIG. 2, a silicon layer with a thickness of approximately 500 layers is deposited on the Hall element 11i3 and its surrounding area by the CVD method.
O
A metal material such as Au/Ge/Ni alloy is deposited on Vl to form an electrode 37, and the capacitor 1 is connected to the electrode 37 and the Hall terminals Vl, V2 and 5i (h film 36).
7.18 has been formed. One end of the capacitor 17, 18 on the electrode 37 side is connected to the detection line 19 or 20, respectively, as shown in FIG. and,
The detection lines 19,20 are connected to a detection circuit as shown in FIG.

The detection circuit is the external detection circuit 2 explained in the section of means above.
1, that is, it has operational amplifiers 24 and 25 in which capacitors 22 and 23 are used as feedback impedances, and an amplifier 26 is used in the final output stage.

Next, the operation of the magnetic sensor according to this embodiment will be explained using FIG.

S+, Ss, S- are switching transistors 15
The gate voltage waveforms of V1, V22, VI2, Vat, V13, . via is hole g
Figure 1 shows the voltage waveforms of V + r, V z r, etc. in order from the middle layer, and VA, V, , V, . There is. Then, to-t@ sets the gate voltage of the first switching transistor 15 to a high level, and the time when this switching transistor 15 is turned on is set to to, and the time is displayed based on this 70.

For example, when the first switching transistor 15 is turned on by a control signal from the shift register 33 (S, in FIG. 4), a constant current I is applied to the Hall element 11 connected to the switching transistor 15 that is turned on. flows, and a voltage fluctuation occurs at the Hall terminal ■ and Vat by adding a voltage proportional to the magnetic flux density at that time to the offset voltage (Fig. 4 V0, ■□).
~tr), other switching transistors 15 are OFF
state (S, , S, in Figure 4), other Hall terminals (V+i, Vxz, V+-, Vis) Niha T1
1 pressure fluctuation does not occur, therefore, the detection line 19.20 has a Hall terminal v,,! Only the displacement current of the capacitor due to the fluctuating voltages generated at 3 and V flows. This displacement current is integrated by capacitors 23 and 22 of the detection circuit (FIG. 3) and converted into a voltage.

Hall terminal V0, V x r Upper electrode 37 (17), 3
7 (18) and the capacitors 17 respectively configured between
．． When the capacitance of 18 and the capacitance of capacitor 23.22 as feedback impedance are equal, the output voltage fluctuation of operational amplifier 25.24 V A , V
The voltage fluctuations of m and the Hall terminals Vl+ and ■ are equal to each other. Therefore, the difference in output voltage fluctuation between the operational amplifier 25 and the operational amplifier 24 (vA-V
If B) is obtained using the differential amplifier 26 with a gain of 1, its special value is the difference in voltage between the Hall terminals Vll and V21, that is, the Hall voltage proportional to the magnetic flux density generated by the Hall effect.

When the switching transistor 15 is turned off,
The state before the switching transistor 15 is turned on is reached, and a reverse voltage fluctuation occurs at the Vth Hall terminal, Vat, so that the detection voltage returns to the voltage before the switching transistor 15 is turned on.

Similarly, by sequentially turning on the primary Hall elements 11, the magnetic flux density of each Hall element 11 can be detected.

As detailed above, in the magnetic sensor according to the present invention, in which two or more Hall elements are arranged on the same substrate, at least one of the current terminals of the Hall elements on the sides A switch is connected to one side, and a detection line is connected to each Hall terminal via a capacitor, so the number of bonding butts for external connection, which had limited the density of Hall elements, is reduced, and the Hall terminal It becomes possible to arrange the elements at a high density, and it is possible to detect the magnetic flux density distribution with high precision. Therefore, brushless D
D-motor control or angle detection of rotating parts of precision equipment can be controlled or detected with high precision6.
By reducing the number of bonding pads, the magnetic sensor itself can be made smaller, which is also effective in reducing the size and weight of control or detection equipment.

[Brief explanation of drawings]

Fig. 1 is a plan view showing an embodiment of the magnetic sensor according to the present invention, Fig. 2 is a sectional view of the Hall element section, Fig. 3 is an external detection circuit diagram, and Fig. 4 explains the operation of the magnetic sensor. FIG. 5 is a circuit diagram for explaining the means according to the present invention, and FIG. 6 is a plan view showing a conventional magnetic sensor. 11... Hall element, 15... Switching transistor (switch), 17.18... Capacitor 19
．． 20...Detection line, 30."Si substrate (substrate) It,
Iz...Current terminal, V+, V*...Hall terminal

Claims (1)

[Claims] (1) In a magnetic sensor in which two or more Hall elements are arranged on a substrate, a switch is connected to at least one of the current terminals of each Hall element, and each Hall terminal is detected via a capacitor. A magnetic sensor characterized in that it is connected to a wire.