Single Op-Amp SQUID Flux-Locking Feedback Circuit
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Solution Overview
Problem
Conventional SQUID flux-locked loops have limited bandwidth and slew-rate due to the use of multiple amplifier stages and integrator circuits, leading to signal delay, phase-shift, and high power consumption, which complicates the design and reduces the performance of magnetic sensors, especially in multi-channel systems.
Innovation Solution
A magnetic sensor using a single low-noise operational amplifier to form an open-loop feedback circuit, eliminating the need for preamplifiers and integrators, thereby increasing bandwidth and slew-rate while simplifying the design and reducing power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple amplifier stages and integrator circuits are used in conventional SQUID flux-locked loops, then the circuit can achieve stable operation and flux locking, but the bandwidth and slew-rate are limited, and power consumption increases
Solution Approach 1:
The patent combines the functions of multiple amplifier stages and integrator circuits into a single operational amplifier configured as a transimpedance amplifier. This single amplifier directly converts SQUID current output to voltage while providing necessary gain and bandwidth, eliminating the need for separate amplifier stages and integrators. The merging of these functions resolves the contradiction by maintaining flux locking stability through the transimpedance configuration while achieving higher bandwidth and slew-rate without the limitations of cascaded stages.
Solution Approach 2:
The single operational amplifier in the patent performs multiple functions simultaneously: it acts as a transimpedance converter, provides signal amplification, and enables flux locking feedback. This multi-functional design replaces the conventional multi-stage architecture where separate components performed these functions sequentially. By making the operational amplifier universal in its capabilities, the circuit achieves stable operation with improved speed characteristics and reduced power consumption.
2Reliability
If multiple amplifier stages and integrator circuits are used in conventional SQUID flux-locked loops, then the circuit can achieve stable operation, but the design becomes complex and power consumption increases
Solution Approach 1:
The patent merges multiple discrete circuit components (preamplifier, integrator, feedback circuitry) into a single operational amplifier-based transimpedance amplifier. This consolidation dramatically reduces the number of components and interconnections required, simplifying the overall circuit design while maintaining flux locking stability through the inherent feedback mechanism of the transimpedance configuration.
Solution Approach 2:
The patent extracts and eliminates unnecessary intermediate stages (separate preamplifier and integrator circuits) from the conventional flux-locked loop design. By removing these redundant components and retaining only the essential transimpedance amplification function in a single operational amplifier, the design complexity is reduced while the core flux locking functionality is preserved.
3Reliability
If multiple amplifier stages and integrator circuits are used in conventional SQUID flux-locked loops, then the circuit can achieve stable operation, but power consumption increases
Solution Approach 1:
The patent combines multiple power-consuming amplifier stages into a single operational amplifier circuit. By consolidating the preamplifier, integrator, and feedback amplification functions into one device, the total power consumption is reduced while maintaining the necessary gain and stability for flux locking operation. The single operational amplifier requires less total power than multiple cascaded stages would require.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution achieves faster tracking speed, higher bandwidth, and lower power consumption, enhancing the performance and miniaturization of SQUID magnetic sensors without lock failure, particularly in multi-channel applications.
Implementation Method 1
the other end of the feedback resistor connects to a feedback coil that is coupled through mutual inductance with the SQUID so as to generate feedback magnetic flux
Implementation Method 2
the voltage across the SQUID will vary as a function of magnitude of external magnetic flux detected by superconducting ring due to superconducting quantum effect and Josephson Effect
Implementation Method 3
the voltage across the SQUID will vary as a function of magnitude of external magnetic flux detected by superconducting ring due to superconducting quantum effect and Josephson Effect
Data Source
AI summary
A magnetic sensor for superconducting quantum interference device using single operational amplifier comprising SQUID, a feedback coil, feedback resistor and an operational amplifier. The voltage signal of SQUID is delivered to one input of the operational amplifier, a bias voltage is delivered to other input of the operational amplifier, and the output of the operational amplifier connects to one end of a feedback resistor, the other end of the feedback resistor connects to a feedback coil that is coupled through mutual inductance with the SQUID so as to generate feedback magnetic flux, the output voltage of the operational amplifier drives the feedback resistance to generate current, thereby forming a flux locking loop. The present invention uses an open loop operational amplifier to implement SQUID magnetic flux locking feedback circuit which simplifies the circuit configuration, decrease the loop delay and thereby achieving higher bandwidth of the flux locking loop.