Low Noise Biasing for Magnetic-Resistance Sensors
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Solution Overview
Problem
Conventional biasing schemes for magneto-resistive (MR) sensors in magnetic storage systems introduce noise that amplifies with increasing areal density and decreasing magnetic field strength, necessitating a low-noise bias generation method.
Innovation Solution
The proposed solution involves a preamplifier circuit with a feedback resistive element and a feedback control circuit that locates noisy bias generating circuitry at the post-amplification side of the feedback loop, using a feedback control circuit to provide bias current or voltage to the MR sensor, and optionally supplementing with additional bias sources if necessary.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional biasing schemes are used for MR sensors, then the bias current or voltage can be provided to the sensor, but noise is introduced that amplifies with increasing areal density
Solution Approach 1:
The patent segments the biasing function into two independent circuits: a low-noise bias circuit that provides the primary bias current/voltage to the MR sensor, and a separate feedback control circuit that adjusts the bias level. This segmentation isolates the noise-sensitive biasing function from the noisy feedback control circuitry, preventing feedback noise from coupling into the sensor signal path.
Solution Approach 2:
The patent extracts the noise-generating components (feedback control circuitry, resistors, capacitors) from the direct signal path to the MR sensor. By placing these components in a separate feedback loop that controls the bias level indirectly, the harmful noise factors are taken out of the primary signal detection path, thereby reducing their impact on measurement precision.
2Quantity of substance
If areal density increases, then data storage capacity improves, but magnetic field strength decreases requiring more precise biasing
Solution Approach 1:
The patent implements a feedback control circuit that continuously monitors the bias level applied to the MR sensor and adjusts the bias current/voltage accordingly. This feedback mechanism ensures precise bias control even as areal density increases and magnetic field strengths decrease, maintaining optimal sensor operation across varying storage densities.
Solution Approach 2:
The patent makes the biasing system dynamic by allowing the bias level to be adjusted in real-time through the feedback control circuit. This dynamic adjustment capability enables the system to adapt to changing operating conditions associated with different areal densities, ensuring consistent measurement precision across a range of storage capacities.
Data Source
AI summary
Circuits, systems, and methods for generating bias for a magneto-resistive (MR) sensor in a magnetic storage device. The circuits generally include an amplifier having an input coupled to a magneto-resistive (MR) sensor, a feedback resistive element having an output coupled to the MR sensor, and a feedback control circuit having a first input coupled to an output of the amplifier, an output coupled to an input of the feedback resistive element, and a second input coupled the output of the feedback resistive element, wherein the feedback control circuit is configured to provide a bias current to the MR sensor through the feedback resistive element. The methods generally include amplifying a signal from the MR sensor to produce an amplified signal, producing a feedback signal from the amplified signal, the feedback signal having a predetermined bias characteristic, and applying the feedback signal to the MR sensor. The systems generally include those that embody one or more of the inventive concepts disclosed herein. The present invention advantageously provides for low noise output from the preamplifier by locating all or most of the potentially noisy bias generating circuitry at the post-amplification side of the feedback loop.