Cryogenic Voltage Reference Using SET Coulomb Blockade
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Solution Overview
Problem
Conventional bandgap voltage reference circuits are unsuitable for low-temperature electronics due to diffusion-dominated currents that are suppressed at temperatures below 50 K, and Josephson effect-based circuits are complex and require advanced control electronics.
Innovation Solution
A method and generator using two single-electron transistors (SETs) connected in series, operated at different Coulomb peaks but with the same slope type, to generate a stable reference voltage based on the difference between their gate-to-source voltages, which is independent of temperature variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If conventional bandgap voltage reference circuits are used, then stable reference voltage is provided at room temperature, but the circuits become non-functional at low temperatures below 50 K due to diffusion-dominated current suppression
Solution Approach 1:
The patent changes the fundamental operating mechanism from diffusion-dominated current (bandgap) to tunneling-dominated current (Coulomb blockade). By operating SETs in the Coulomb blockade regime where tunneling current dominates over diffusion current, the reference voltage generator maintains functionality and stability at cryogenic temperatures where conventional bandgap circuits fail.
Solution Approach 2:
The patent substitutes the thermal diffusion mechanism with a quantum tunneling mechanism. Instead of relying on thermally activated carrier diffusion that ceases at low temperatures, the invention uses electron tunneling through potential barriers in single-electron transistors, which remains effective and controllable at cryogenic temperatures.
2Temperature
If Josephson effect-based circuits are used for low-temperature voltage generation, then stable voltage can be generated at cryogenic temperatures, but the circuits become complex and require advanced control electronics
Solution Approach 1:
The patent extracts and eliminates the complex control electronics requirement from the system. By using SETs operated in the Coulomb blockade regime with simple voltage division and comparison circuits, the invention achieves cryogenic temperature operation without needing the sophisticated control electronics that Josephson junction-based systems require.
Solution Approach 2:
The patent employs simpler, more readily available single-electron transistor components instead of complex Josephson junction assemblies. The SET-based approach uses standard semiconductor fabrication techniques and requires basic voltage control circuits, making the system more accessible and less complex than Josephson effect-based solutions.
3Power
If two SETs are operated at different Coulomb peaks with different slope types, then voltage difference can be generated, but temperature variations cause instability in the reference voltage
Solution Approach 1:
The patent deliberately creates asymmetry by operating the two SETs at different Coulomb peaks (different voltage levels) while maintaining symmetry in the slope type selection. This asymmetric voltage positioning with symmetric slope characteristics enables temperature compensation, as the identical slope types ensure that temperature-induced voltage drifts affect both SETs equally and cancel out in the differential measurement.
Solution Approach 2:
The patent implements a feedback mechanism where the voltages from both SETs are compared and processed to generate the reference voltage. The system monitors the voltage outputs and uses the differential comparison to cancel temperature-dependent variations, ensuring stable reference voltage output despite temperature fluctuations.
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
Provides a stable reference voltage suitable for low-temperature electronics, such as cryogenic applications, without the complexity of Josephson effect-based circuits and operational at temperatures where conventional bandgap circuits fail.
Implementation Method 1
If a SET is operated in the Coulomb blockade regime, the drain-to-source current through the SET may oscillate as a function of applied gate-to-source voltage and give rise to so called Coulomb peaks.
Data Source
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AI summary
The present disclosure provides a method of generating a reference voltage, including providing a first single-electron transistor (SET, 110) and a second SET (120) connected in series with the first SET, biasing the first SET and the second SET using a same biasing current (Ib), operating the first SET at a slope of a first Coulomb peak (210), wherein the slope of the first Coulomb peak is of a slope type selected from a rising slope (211r), a peak maximum (211m), and a falling slope (211f), operating the second SET at a slope of a second Coulomb peak (220) different from the first Coulomb peak, wherein the slope of the second Coulomb peak is of the same slope type as the slope of the first Coulomb peak, and generating the reference voltage (Vref) based on a difference between a gate-to-source voltage (Vgs1) of the first SET and a gate-to-source voltage (Vgs2) of the second SET. A reference voltage generator (100) is also provided.