JPH0418777A - Semiconductor device - Google Patents

Abstract

PURPOSE:To enable a magnetic flux to be surely and accurately detected by a method wherein a Hall sensor which outputs an inbalanced voltage when a magnetic flux is not existing and a differential amplifier which amplifies a Hall electromotive force outputted from the Hall sensor are provided. CONSTITUTION:A current source 12 is connected to the current injection electrode of a Hall sensor 11, and the other electrode opposed to the electrode concerned is grounded. A power is supplied to the current source 12 from a power supply voltage VDD, and a constant current is made to flow downward through the Hall sensor from above as shown on a figure. A pair of electrodes 11a and 11b are asymmetrically arranged on the side face of the Hall sensor 11 so as to take out a Hall electromotive force induced through Hall effect. The electrodes 13a and 13b are connected to differential input terminals 13a and 13b of a differential amplifier 13 provided with a common source. The differential amplifier 13 amplifies the difference between voltages inputted into the input terminals 13a and 13b and outputs the amplified voltage difference to an output terminal 13c. The electrodes 11a and 11b are asymmetrically disposed so as to absorb and cancel an offset voltage induced between the input terminals 13a and 13b of the differential amplifier 13 and to make the output of the differential amplifier 13 negative.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a semiconductor device using a Hall sensor that detects magnetic flux and converts it into an electrical signal.

[Conventional technology]

Conventionally, a typical semiconductor device using this type of Hall sensor has a circuit configuration shown in FIG. 3, for example. A constant current is supplied to the Hall sensor 1 from a current source 2. When external magnetic flux acts on this Hall sensor 1, terminal la is activated.

A Hall electromotive force (Hall voltage) is generated between lb and lb. This end f vs. 1a, 1. b are arranged symmetrically, and the Hall electromotive force generated between the terminals is transferred to the input terminal 3a of the differential amplifier 3.
, 3b, amplified, and outputted to the output terminal 3c.

[Problems that the invention attempts to solve 17] However, the input terminal 3a of the differential amplifier 3.

3b, an offset voltage always occurs between each input terminal 3a.
, 3b, the voltage is output to the output terminal 3C even if the differential input voltages are exactly the same value. As a result, an output voltage may appear from the differential amplifier 3 even when there is no magnetic flux in the Hall sensor 1, or conversely, an output voltage may not appear at the differential amplifier 3 even though there is magnetic flux. A phenomenon occurs.

The magnetic flux detection output appearing at the output terminal T-3c of the differential amplifier 3 originally has the detection characteristics shown in FIG. 4.

In other words, the magnetic field [Gaussl is 0
When , the output voltage [V] shown on the vertical axis should originally be O. However, due to the offset voltage generated between the input terminals 3a and 3b of the differential amplifier 3, the detection characteristics become as shown in FIG. In other words, even when the magnetic field [Gaussl] shown on the horizontal axis in the figure is 0, the output voltage [V] shown on the vertical axis is
orl'set.

[Means to solve the problem]

The present invention was made to solve such problems, and includes a Hall sensor that outputs an unbalanced voltage when there is no magnetic flux because the electrode plate 1 that extracts the Hall electromotive force is arranged asymmetrically, and the output from this Hall sensor. J1η is constructed from a differential amplifier that amplifies the Hall electromotive force generated.

[Effect]

The offset voltage created between the input terminals of the differential amplifier is canceled out by the unbalanced voltage output by the asymmetric electrode pair structure of the Hall sensor.

〔Example〕

FIG. 1 shows a semiconductor device using a Hall sensor according to an embodiment of the present invention.

A current source 12 is connected to a current injection electrode of the Hall sensor 11, and the other electrode facing this electrode is grounded. The current source 12 receives power from the power supply voltage Vl)D, and supplies a constant current to the Hall sensor 1 from one side in the figure downward. Further, on the side surface of the Hall sensor 11, electrode pairs 1.1a, 11. b are arranged asymmetrically. This electrode pair 1.1. a and llb are connected to differential input terminals 13a and 13b of a differential amplifier 13 having a common source. The differential amplifier 13 amplifies the voltage difference input to these input terminals 13a and 13b and outputs it to an output terminal 13c. This differential amplifier 13 also has a power supply voltage VD
It operates by power supply from D.

The positional relationship between the electrode pair 11a and llb is based on the ball sensor 11.
It is determined by the magnitude of the current flowing through the hole sensor and the specific resistance of the Hall sensor. In this embodiment, the differential amplifier 13
The rgWIJs 11a and 11b are arranged asymmetrically so that offset voltages generated at the input terminals 13a and 13b of the rgWIJs are absorbed and canceled, and further, the output of the differential amplifier 13 swings to the negative side.

In addition, by newly providing another current source and adjusting the current amount of this current source, electrode pair 1. ], a1, 1 b
It is also possible to arbitrarily set the value of the unbalanced voltage that occurs in i+J.
It is Noh.

The magnetic flux detection characteristics of the device with such a configuration are shown in FIG. In the figure, the horizontal axis represents the strength of the magnetic field applied to the Hall sensor 11 [Gaussl], and the vertical axis represents the detected voltage [V] appearing at the output terminal 13c of the differential amplifier 13. Electrode pair 11a, 11. Due to the asymmetric structure of b, even when no magnetic field is applied to the Hall sensor 1], the output terminal],
A voltage value -Va due to the reverse offset appears at 3c.

When a magnetic field with a strength exceeding the unbalanced voltage generated on the electrode pair 1.1a, llb is applied to the Hall sensor 11, the output of the differential amplifier 13 swings to the 1■- side, and the magnetic flux acting on the Hall sensor 11 Detected. Note that this device digitally detects the presence or absence of magnetic flux.

In this embodiment, the magnetic flux is
1, the output terminal 1 of the differential amplifier 13
No detection output appears at 3c, and there is no possibility of erroneously detecting magnetic flux as in the conventional case. Therefore, the presence or absence of magnetic flux acting on the Hall sensor 11 can be accurately determined.

In addition, in the explanation of the above embodiment, the device was used digitally, but if the output of the differential amplifier 13 due to unbalanced voltage is set to O without swinging to the negative side, it is possible to use the device analogously. It is. In this case as well, effects similar to those of the above embodiment can be obtained.

[Effects of the Invention] As described above, according to the present invention, the offset voltage generated between the input terminals of the differential amplifier is canceled out by the unbalanced voltage output by the asymmetric electrode pair structure of the Hall sensor. For this reason, even when there is no magnetic flux in the Hall sensor, an output voltage appears from the differential amplifier as in the conventional case, and conversely, even when there is no magnetic flux, the output voltage appears at the differential amplifier. The phenomenon that magnetic flux does not appear will disappear, and it will become possible to provide a device that can accurately detect magnetic flux.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing the configuration of a semiconductor device using a Hall sensor according to an embodiment of the present invention, FIG. 2 is a graph showing magnetic flux detection characteristics of the semiconductor device according to the embodiment shown in FIG. 1, and FIG. Fig. 3 is a circuit diagram showing the configuration of a conventional semiconductor device using a Hall sensor, Fig. 4 is a graph showing the magnetic flux detection characteristics that this type of device should originally have, and Fig. 5 is a circuit diagram showing the configuration of a conventional semiconductor device using a Hall sensor. It is a graph showing magnetic flux detection characteristics of the device. DESCRIPTION OF SYMBOLS 11...Hall sensor, l]a, llb...Asymmetrically arranged electrode pair, 12...Current source, 13...Differential amplifier, 13a, 13b...Differential input terminal, 1.3
c ・Detection output terminal. Characteristics of Honte・1st life Diagram 4 Characteristics of the next generation

Claims (1)

[Claims] A Hall sensor that outputs an unbalanced voltage when there is no magnetic flux because the electrode pair that extracts the Hall electromotive force is arranged asymmetrically,
A semiconductor device comprising a differential amplifier that amplifies the Hall electromotive force by canceling an offset voltage by the unbalanced voltage output from the Hall sensor.