Current bias, current sense for magneto-resistive preamplifier, preamplifying integrated circuit, and related methods
First Claim
1. A preamplifier for a hard disk drive, the preamplifier comprising:
- a magneto-resistive (MR) sensor responsive to a current bias for sensing a change in magnetic data flux and responsively providing a change in electrical resistance;
preamplifying means connected to a supply voltage and to said MR sensor for providing a current bias to said MR sensor and for amplifying a detected change in electrical resistance from said MR sensor, said preamplifying means including a current-source sensor biasing circuit for providing a desired biasing current to said MR sensor and an amplifying output circuit connected to said current-source sensor biasing circuit for providing an amplified output signal representative of the detected change in biasing current supplied to said MR sensor due to the change in electrical resistance, the current-source sensor biasing circuit including a current source for generating a source current, a first amplifying circuit connected to said MR sensor and to a supply voltage for sensing the change in electrical resistance from said MR sensor, a second amplifying circuit having a first input connected to the first amplifying circuit and a second input connected to the current source, and a transconductance amplifying circuit having first and second differential inputs respectively connected to first and second outputs of the second amplifying circuit and having an output connected to the first amplifying circuit for providing an output current proportional to the voltage difference at the first and second inputs thereof; and
stabilizing means connected to said preamplifying means and to ground for stabilizing at least a portion of said preamplifying means.
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Accused Products
Abstract
A current bias, current sense magneto-resistive preamplifier for a hard disk drive and related methods preferably includes an MR sensor responsive to a current bias for sensing a change in magnetic data flux and responsively providing a change in electrical resistance. A preamplifying circuit is preferably connected to the MR sensor for providing the current bias thereto and for amplifying a detected change in electrical resistance. The preamplifying circuit includes a sensor biasing circuit for providing the current bias to the MR sensor and an amplifying output circuit for providing an amplified output signal representative of the detected change in current bias to the MR sensor. The sensor biasing circuit preferably includes a current source, a first amplifying circuit connected to the MR sensor for sensing the change in electrical resistance therefrom, and a second amplifying circuit having a first input connected to the first amplifying circuit and a second input connected to the current source. The sensor biasing circuit also includes a transconductance amplifying circuit connected to first and second outputs of the second amplifying circuit and having an output connected to the first amplifying circuit for providing an output current proportional to the voltage difference at the first and second inputs thereof. The preamplifier further includes a capacitor connected to the preamplifying circuit for providing stability to at least a portion of the preamplifying circuit.
60 Citations
27 Claims
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1. A preamplifier for a hard disk drive, the preamplifier comprising:
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a magneto-resistive (MR) sensor responsive to a current bias for sensing a change in magnetic data flux and responsively providing a change in electrical resistance; preamplifying means connected to a supply voltage and to said MR sensor for providing a current bias to said MR sensor and for amplifying a detected change in electrical resistance from said MR sensor, said preamplifying means including a current-source sensor biasing circuit for providing a desired biasing current to said MR sensor and an amplifying output circuit connected to said current-source sensor biasing circuit for providing an amplified output signal representative of the detected change in biasing current supplied to said MR sensor due to the change in electrical resistance, the current-source sensor biasing circuit including a current source for generating a source current, a first amplifying circuit connected to said MR sensor and to a supply voltage for sensing the change in electrical resistance from said MR sensor, a second amplifying circuit having a first input connected to the first amplifying circuit and a second input connected to the current source, and a transconductance amplifying circuit having first and second differential inputs respectively connected to first and second outputs of the second amplifying circuit and having an output connected to the first amplifying circuit for providing an output current proportional to the voltage difference at the first and second inputs thereof; and stabilizing means connected to said preamplifying means and to ground for stabilizing at least a portion of said preamplifying means. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A preamplifier for a hard disk drive, the preamplifier comprising:
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a magneto-resistive (MR) sensor responsive to a current bias for sensing a change in magnetic data flux and responsively providing a change in electrical resistance; and a preamplifying integrated circuit connected to a supply voltage and to said MR sensor for providing a current bias to said MR sensor and for detecting the change in electrical resistance from said MR sensor, said preamplifying integrated circuit including a current-source sensor biasing circuit for providing the current bias to said MR sensor and an amplifying output circuit connected to said current-source sensor biasing circuit for providing an amplified output signal representative of the change in current bias to said MR sensor due to the change in electrical resistance, the current-source sensor biasing circuit including a current source connected to ground and a supply voltage for generating a source current and a current biasing loop circuit for sensing a change in the biasing current responsive to a change in the electrical resistance of said MR sensor, the current biasing loop circuit comprising a first amplifying circuit connected to said MR sensor and to a supply voltage for biasingly driving said MR sensor so as to provide the change in electrical resistance, a second amplifying circuit having a first input connected to the first amplifying circuit and a second input connected to the current source, and a transconductance amplifying circuit having first and second inputs respectively connected to first and second outputs of the second amplifying circuit and having an output connected to the first amplifying circuit for providing an output current proportional to the voltage difference at the first and second inputs thereof, the output current driving the first amplifying circuit so as to bias said MR sensor. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 18)
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19. A preamplifying integrated circuit adapted to be connected to a supply voltage and to a magneto-resistive (MR) sensor for providing a current bias to the MR sensor and for detecting the change in electrical resistance from the MR sensor, the integrated circuit comprising:
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a substrate; a current-source sensor biasing circuit formed on said substrate for providing the current bias to the MR sensor, the current-source sensor biasing circuit including a current source for generating a source current and a current biasing loop circuit responsive to said current source for providing the biasing current to an MR sensor and for sensing a change in the biasing current responsive to a change in the electrical resistance of the MR sensor, the current biasing loop circuit comprising a first amplifying circuit adapted to be connected to an MR sensor for biasingly driving the MR sensor so as to detect the change in electrical resistance, a second amplifying circuit having a first input connected to the first amplifying circuit and a second input connected to the current source, and a transconductance amplifying circuit having first and second inputs respectively connected to first and second outputs of the second amplifying circuit and having an output connected to the first amplifying circuit and adapted to be connected to an external capacitor for providing an output current proportional to the voltage difference at the first and second inputs thereof, the output current driving the first amplifying circuit so as to bias the MR sensor; and an amplifying output circuit formed on said substrate and connected to the current-source sensor biasing circuit for providing an amplified output signal representative of the change in current bias to the MR sensor due to the change in electrical resistance. - View Dependent Claims (20, 21, 22, 23)
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24. A method of biasing a magneto-resistive (MR) sensor so as to detect a change in the electrical resistance of the MR sensor, the method comprising the steps of:
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generating a reference voltage responsive to a source current and a supply, voltage; providing a first amplifying circuit responsive to the supply voltage to thereby generate an initial biasing voltage so as to supply an initial biasing current across the MR sensor and to thereby amplify a sensed change in the biasing current; providing a second amplifying circuit having first and second inputs respectively connected to the reference voltage and the initial biasing voltage to amplify a difference between the reference voltage and the initial biasing voltage; and providing a transconductance amplifier connected to the first amplifying circuit and the outputs of the second amplifying circuit to thereby generate a driving current for the first amplifying circuit proportional to the determined voltage difference between the reference voltage and the initial biasing voltage so that the first amplifying circuit supplies a desired biasing current across the MR sensor. - View Dependent Claims (25, 26, 27)
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Specification