Temperature compensated Hall-effect sensor apparatus
First Claim
1. A Hall-effect sensor for producing an electrical signal corresponding to magnetic flux density, comprising:
- a Hall-effect element having bias electrodes for supply of bias voltage to the Hall-effect element and output electrodes at which an output voltage is produced, the output voltage having an offset voltage component and a signal voltage component;
voltage regulator means having a pair of output terminals connected to the bias electrodes and operative for supplying a regulated voltage to the bias electrodes, the regulated voltage being maintained at a substantially constant value independent of load and ambient temperature variations, thereby producing an offset voltage component that is substantially constant and independent of variations in ambient temperature and a sensitivity ratio between the signal voltage component and the magnetic flux density that is decreasing function of temperature, the voltage regulator means including a band gap regulator for supplying the regulated voltage to the bias electrodes; and
a measuring circuit including amplifier means having an input coupled to the output electrodes, wherein the amplifier means includes;
a differential amplifier having a gain that decreases as a function of temperature, the differential amplifier including first and second transistors having input electrodes connected to the output electrodes of the Hall-effect element and first and second resistors connected in series with the first and second transistors;
andgain compensation means to increase the amplification of the amplifier means, thereby compensating for the gain reduction of the differential amplifier as a function of temperature and providing an amplifier gain that is substantially independent of variations in temperature, the gain compensation means including a third transistor having an input electrode to which the regulated voltage is applied and a third resistor in series with the third transistor, the third transistor being arranged for control of current through both the first and second transistors;
wherein the first and second resistors can be adjusted relative to each other to null out the voltage offset of the Hall-effect element and the third resistor can be adjusted to provide a desired sensitivity ratio between the between the signal voltage component and the magnetic flux density.
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Accused Products
Abstract
A temperature compensated Hall-effect sensor apparatus is disclosed which senses the position of a moving body and provides an output signal indicative of the position of the moving body. The apparatus includes a Hall device which senses the application and subsequent removal of a magnetic field and provides an output signal to a constant gain amplifier. Circuitry is provided in the constant gain amplifier for adjusting the gain of the amplifier and also for nulling-out any offset voltage received from the Hall device. The output of the constant gain amplifier is input to a sensitivity compensation and hysteresis circuit for setting a positive-going threshold trip level and a negative-going threshold trip level into a comparator. Circuitry is included which provides both the positive-going and the negative-going threshold trip levels with temperature compensation such that the effective positive and negative trip levels of the comparator remain the same for a given magnetic field and are independent of the temperature of or the signal level out of the Hall device as affected by temperature. Circuitry is provided to change the amount of hysteresis such that the negative-going threshold trip level is a predetermined percentage of the positive-going threshold trip level. The apparatus has a fixed hysteresis ratio.
144 Citations
20 Claims
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1. A Hall-effect sensor for producing an electrical signal corresponding to magnetic flux density, comprising:
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a Hall-effect element having bias electrodes for supply of bias voltage to the Hall-effect element and output electrodes at which an output voltage is produced, the output voltage having an offset voltage component and a signal voltage component; voltage regulator means having a pair of output terminals connected to the bias electrodes and operative for supplying a regulated voltage to the bias electrodes, the regulated voltage being maintained at a substantially constant value independent of load and ambient temperature variations, thereby producing an offset voltage component that is substantially constant and independent of variations in ambient temperature and a sensitivity ratio between the signal voltage component and the magnetic flux density that is decreasing function of temperature, the voltage regulator means including a band gap regulator for supplying the regulated voltage to the bias electrodes; and a measuring circuit including amplifier means having an input coupled to the output electrodes, wherein the amplifier means includes; a differential amplifier having a gain that decreases as a function of temperature, the differential amplifier including first and second transistors having input electrodes connected to the output electrodes of the Hall-effect element and first and second resistors connected in series with the first and second transistors; and gain compensation means to increase the amplification of the amplifier means, thereby compensating for the gain reduction of the differential amplifier as a function of temperature and providing an amplifier gain that is substantially independent of variations in temperature, the gain compensation means including a third transistor having an input electrode to which the regulated voltage is applied and a third resistor in series with the third transistor, the third transistor being arranged for control of current through both the first and second transistors; wherein the first and second resistors can be adjusted relative to each other to null out the voltage offset of the Hall-effect element and the third resistor can be adjusted to provide a desired sensitivity ratio between the between the signal voltage component and the magnetic flux density.
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2. A Hall-effect sensor for producing an electrical signal corresponding to magnetic flux density, comprising:
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a Hall-effect element having bias electrodes for supply of bias voltage to the Hall-effect element and output electrodes at which an output voltage is produced, the output voltage having an offset voltage component and a signal voltage component; voltage regulator means having a pair of output terminals connected to the bias electrodes and operative for supplying a regulated voltage to the bias electrodes, the regulated voltage being maintained at a substantially constant value independent of load and ambient temperature variations, thereby producing an offset voltage component that is substantially constant and independent of variations in ambient temperature and a sensitivity ratio between the signal voltage component and the magnetic flux density that is a decreasing function of temperature; and a differential amplifier including first and second transistors having input electrodes connected to the output electrodes of the Hall-effect element, a third transistor connected in series with the first and second transistors to control the total current through the first and second transistors, and conductance control means for control of the third transistor to obtain an amplifier gain that is substantially independent of changes in ambient temperature; wherein the conductance control means includes a resistor that can be adjusted to provide a desired sensitivity ratio between the signal voltage component and the magnetic flux density, a fourth transistor having a base-emitter junction in parallel with the base-emitter junction of the third transistor, a fifth transistor for supplying current to the parallel-connected base-emitter junctions of the third and fourth transistors, a sixth transistor having a base-emitter junction in parallel with the base-emitter junction of the fifth transistor, and a seventh transistor and having a control electrode to which the regulated voltage is applied, each of the first, second, fifth and sixth transistor being of one conductive type and each of the third, fourth and seventh transistors being of a conductive type that is complementary to the one conductive type; and wherein the resistor is connected in series with the seventh transistor. - View Dependent Claims (3, 4, 5, 6)
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7. A Hall-effect sensor for producing an electrical signal corresponding to magnetic flux density, comprising:
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a Hall-effect element having bias electrodes for supply of bias voltage to the Hall-effect element and output electrodes at which an output voltage is produced, the output voltage having an offset voltage component and a signal voltage component; voltage regulator means having a pair of output terminals connected to the bias electrodes and operative for supplying a regulated voltage to the bias electrodes, the regulated voltage being maintained at a substantially constant value independent of load and ambient temperature variations, thereby producing an offset voltage component that is substantially constant and independent of variations in ambient temperature and a sensitivity ratio between the signal voltage component and the magnetic flux density that is decreasing function of temperature; and a measuring circuit connected to the output electrodes, the measuring circuit including a comparator having a pair of input terminals, amplifier means for amplifiying signals developed at the output electrodes and applying the amplified signals to the input terminals of the comparator, a resistor connected in series with one of the input terminals of the comparator, shunt transistor means coupled in a shunt relationship with the input terminals of the comparator, the comparator being switched from a first state to a second state at a positive trip level that is a function of the resistance value of the resistor, and control means coupled to the output of the comparator and arranged to control the shunt transistor means to provide hysteresis with the comparator being switched from the second state to the first state at a desired negative trip level. - View Dependent Claims (8, 9, 10, 11, 12)
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13. The Hall-effect sensor for producing an electrical signal corresponding to magnetic flux density, comprising:
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a Hall-effect element having bias electrodes for supply of bias voltage to the Hall-effect element and output electrodes at which an output voltage is produced, the output voltage having an offset voltage component and a signal voltage component; voltage regulator means having a pair of output terminals connected to the bias electrodes and operative for supplying a regulated voltage to the bias electrodes, the regulated voltage being maintained at a substantially constant value independent of load and ambient temperature variations, thereby producing an offset voltage component that is substantially constant and independent of variations in ambient temperature and a sensitivity ratio between the signal voltage component and the magnetic flux density that is a decreasing function of temperature; and amplifier means having offset voltage compensation means for compensating for the offset voltage of the Hall-effect element, the amplifier means including a pair of transistors having input electrodes connected to the output electrodes of the Hall-effect element and a pair of resistors connected in series with the transistors, the resistance values of the resistors being adjustable relative to each other to provide the offset voltage compensation. - View Dependent Claims (14, 15)
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16. A Hall-effect sensor for producing an electrical signal corresponding to magnetic flux density, comprising:
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a Hall-effect element having bias electrodes for supply of bias voltage to the Hall-effect element and output electrodes at which an output voltage is produced, the output voltage having an offset voltage component and a signal voltage component; voltage regulator means having a pair of output terminals connected to the bias electrodes and operative for supplying a regulated voltage to the bias electrodes, the regulated voltage being maintained at a substantially constant value independent of load and ambient temperature variations, thereby producing an offset voltage component that is substantially constant and independent of variations in ambient temperature and a sensitivity ratio between the signal voltage component and the magnetic flux density that is a decreasing function of temperature; and a differential amplifier including first and second transistors having input electrodes connected to the output electrodes of the Hall-effect element, a third transistor connected in series with the first and second transistors to control the total current through the first and second transistors, and conductance control means for control of the third transistor to obtain an amplifier gain that is substantially independent of changes in ambient temperature; wherein the conductance control means includes a resistor that can be adjusted to provide a desired sensitivity ratio between the signal voltage component and the magnetic flux density. - View Dependent Claims (17, 18)
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19. The Hall-effect sensor for producing an electrical signal corresponding to magnetic flux density, comprising:
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a Hall-effect element having bias electrodes for supply of bias voltage to the Hall-effect element and output electrodes at which an output voltage is produced, the output voltage having an offset voltage component and a signal voltage component; voltage regulator means having a pair of output terminals conencted to the bias electrodes and operative for supplying a regulated voltage to the bias electrodes, the regulated voltage being maintained at a substantially constant value independent of load and ambient temperature variations, thereby producing an offset voltage component that is substantially constant and independent of variations in ambient temperature and a sensitivity ratio between the signal voltage component and the magnetic flux density that is a decreasing function of temperature; and a measuring circuit connected to the output electrodes, the measuring circuit including a detector circuit that operates at controllable threshold levels, a resistor having a resistance value that is a decreasing function of temperature substantially the same as that of the sensitivity ratio, and means for controlling the threshold levels in accordance with the resistance value of the resistor, thereby adjusting the threshold level in proportion to the sensitivity ratio. - View Dependent Claims (20)
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Specification