Current Dynamic Range Research Articles

An Active-Matrix Synaptic Phototransistor Array for In-Sensor Spectral Processing.

The human retina perceives and preprocesses the spectral information of incident light, enabling fast image recognition and efficient chromatic adaptation. In comparison, it is reluctant to implement parallel spectral preprocessing and temporal information fusion in current complementary metal-oxide-semiconductor (CMOS) image sensors, requiring intricate circuitry, frequent data transmission, and color filters. Herein, an active-matrix synaptic phototransistor array (AMSPA) is developed based on organic/inorganic semiconductor heterostructures. The AMSPA provides wavelength-dependent, bidirectional photoresponses, enabling dynamic imaging and in-sensor spectral preprocessing functions. Specifically, near-infrared light induces inhibitory photoresponse while UV light results in exhibitory photoresponse. With rational structural design of the organic/inorganic hybrid heterostructures, the current dynamic range of phototransistor is improved to over 90 dB. Finally, a 32 × 64 AMSPA (128 pixels per inch) is demonstrated with one-switch-transistor and one-synaptic phototransistor (1-T-1-PT) structure, achieving spatial chromatic enhancement and temporal trajectory imaging. These results reveal the feasibility of AMSPA for constructing artificial vision systems.

Pixel-wise exposure control for single-shot HDR imaging: A joint optimization approach

Dynamic range is one of the primary limitations that restricts digital image sensors from acquiring more visual information. Current high dynamic range (HDR) imaging techniques entail a trade-off between dynamic range and visual fidelity. In this work, we propose a HDR imaging method, termed PE-HDR, to achieve both a wide dynamic range and high visual fidelity without additional complex post-processing algorithms. Instead of merging a bracketed exposure sequence, the PE-HDR captures HDR images in a single shot using optical coded pixel-wise exposure control, enabling cost-effective and flexible HDR imaging. By incorporating a differentiable optical encoder and a neural network decoder, we jointly optimize the imaging pipeline from light irradiance to digital image signals, thereby refining the pixel-wise exposure control strategy and improving image fidelity. Both simulations and experiments demonstrate that the proposed method achieves a dynamic range of up to 120 dB and an excellent visual fidelity with spatial resolution of up to 2560 × 1600 pixels.

Study and implementation of fluxgate current sensor with wireless connectivity for finger exoskeleton rehabilitation

SummaryA fully integrated fluxgate magnetometer has been developed to monitor motor current in a finger exoskeleton device. The use of a fluxgate sensor can provide more accurate and natural movement of the fingers, as well as reducing the weight and complexity of the exoskeleton design. The sensor we developed incorporates several advanced features that provide enhanced sensitivity and accuracy compared to existing state‐of‐the‐art sensors. These features include a fluxgate frontend readout circuit with chopping stabilization technology, which achieves a gain of 14.3 V/T, a low noise density of 4.5 nT/√Hz, and a wide measurement range of ±1.5 mT. The gain variation of the sensor is only 1.5% at an 850 kHz bandwidth, and it has a wide dynamic current range from 0.005 mA to 100 A. The sensor also features an integrated 2.4 GHz wireless circuit for easy data transmission. The use of a fluxgate sensor in monitoring motor torque in the proximal interphalangeal joint can provide more precise and natural finger movement and reduce the weight and complexity of the exoskeleton design.

Defective Ru-doped α-MnO2 nanorods enabling efficient hydrazine oxidation for energy-saving hydrogen production via proton exchange membranes at near-neutral pH

Proton exchange membrane water electrolysis (PEMWE) showes substantial advantages over the conventional alkaline water electrolysis (AWE) for power-to-hydrogen (PtH) conversion, given the faster response and wider dynamic current range of the PEMWE technology. However, PEMWE is currently still expensive due partly to the high voltage needed to operate at high current densities and inevitable usage of precious iridium/ruthenium-based catalysts to expedite the slow kinetics of the oxygen evolution reaction (OER) and to ensure sufficient durability under strongly acidic conditions. Herein, we report that ruthenium doped α-manganese oxide (Ru/α-MnO2) nanorods show outstanding electrocatalytic performance toward the hydrazine (N2H4) oxidation reaction (HzOR) in near-neutral media (weak alkaline and weak acid), which can be used to replace the energy-demanding OER for PEMWE. The as-prepared Ru/α-MnO2 is found to comprise abundant defects. When used to catalyze HzOR in the acid-hydrazine electrolyte (0.05 M H2SO4 + 0.5 M N2H4), it can deliver an anodic current density of 10 mA cm−2 at a potential as low as 0.166 V vs. reversible hydrogen electrode (RHE). Moreover, Ru/α-MnO2 exhibits remarkable corrosion/oxidation resistance and remains electrochemically stable during HzOR for at least 1000 h. Theoretical calculations and experimental studies prove that Ru doping elongates the Mn–O bond and produces abundant cationic defects, which induces charge delocalization and significantly lowers material’s electrical resistance and overpotential, resulting in excellent HzOR catalytic activity and stability. The introduction of N2H4 significantly reduces the energy demand for hydrogen production, so that PEMWE can be accomplished under remarkably low voltages of 0.254 V at 10 mA cm−2 and 0.935 V at 100 mA cm−2 for a long term without notable degradation. This work opens a new avenue toward energy-saving PEMWE with earth-abundant OER catalysts.

Near-Full Current Dynamic Range THz Quantum Cascade Laser Frequency Comb.

The present study proposes a terahertz quantum cascade laser frequency comb (THz QCL FC) with a semi-insulated surface plasma waveguide characterized by a low threshold current density, high power and a wide current dynamic range. The gain dispersion value and the nonlinear susceptibility were optimized based on the combination of a hybrid bound-to-continuum active region with a semi-insulated surface plasmon waveguide. Without any extra dispersion compensator, stable frequency comb operation within a current dynamic range of more than 97% of the total was revealed by the intermode beat note map. Additionally, a total comb spectral emission of about 300 GHz centered around 4.6 THz was achieved for a 3 mm long and 150 µm wide device. At 10 K, a maximum output power of 22 mW was obtained with an ultra-low threshold current density of 64.4 A·cm-2.

An Ultra-Low Power Fast Transient LDO with Dynamic Bias

A low-dropout linear regulator (LDO) without external capacitors is designed, combining ultra-low power consumption and ultra-fast transient response. The common support voltage of the LDO is 2.5 V to 3.6 V with a stable output voltage of 1.2 V and an output current dynamic range of 10 μA to 20 mA to supply power to other circuit modules. A Rail-to-Rail Input-Output (RRIO) Class AB push-pull output amplifier and a dynamic bias circuit are also designed. Meanwhile, a dynamic bias circuit which can regulate the operating current of error amplifier is proposed by monitoring output voltage variation in order to provide a larger compensation current to the operational amplifier when the load current changes are at high frequency and maintain ultra-low operating current at low clock frequency. The LDO is designed without resistors, and the deep well NMOS is applied in the output stage in order to reduce the difficulty of loop compensation. Designed in a 180 nm CMOS process, the post-simulation results show that under the condition of 40 °C and 3 V input voltage, the static power consumption is 31.7 nA with a settling time (±5%) of less than 35 ns.

High-precision robust monitoring of charge/discharge current over a wide dynamic range for electric vehicle batteries using diamond quantum sensors

Accurate prediction of the remaining driving range of electric vehicles is difficult because the state-of-the-art sensors for measuring battery current are not accurate enough to estimate the state of charge. This is because the battery current of EVs can reach a maximum of several hundred amperes while the average current is only approximately 10 A, and ordinary sensors do not have an accuracy of several tens of milliamperes while maintaining a dynamic range of several hundred amperes. Therefore, the state of charge has to be estimated with an ambiguity of approximately 10%, which makes the battery usage inefficient. This study resolves this limitation by developing a diamond quantum sensor with an inherently wide dynamic range and high sensitivity for measuring the battery current. The design uses the differential detection of two sensors to eliminate in-vehicle common-mode environmental noise, and a mixed analog–digital control to trace the magnetic resonance microwave frequencies of the quantum sensor without deviation over a wide dynamic range. The prototype battery monitor was fabricated and tested. The battery module current was measured up to 130 A covering WLTC driving pattern, and the accuracy of the current sensor to estimate battery state of charge was analyzed to be 10 mA, which will lead to 0.2% CO2 reduction emitted in the 2030 WW transportation field. Moreover, an operating temperature range of − 40 to + 85 °C and a maximum current dynamic range of ± 1000 A were confirmed.

Novel Resistorless, Cascadable Current-Mode Precision Rectifier Using CFDITA

The paper introduces a new circuit structure of precision full-wave rectifier, without the requirement of any diode(s) and passive component(s), which operates in current mode. The proposed structure of the rectifier employs a single current follower differential input transconductance amplifier and two MOS transistors only. The use of the least number of active components makes the circuit structure simple and favorable to the contemporary integration technology. The proposed rectifier has wider input current dynamic range (±1.6 mA), lower current offset (84 pA), and can operate up to 30 MHz frequency. Additionally, the circuit is easily cascadable, temperature insensitive, and less affected by process variation, MOS transistors mismatch, and supply voltage variation. The rectifier circuit is verified through 0.18 µm gpdk technology-based post-layout simulation results using the cadence Virtuoso tool. The rectification accuracy is examined through the parameters, such as average value ratio and root mean square error. The proposed rectifier’s layout measures 31.95 µm × 31.35 µm in size.

Linear, High Dynamic Range Isolated Skin Resistance Transducer Circuit for Neurophysiological Research in Individuals after Spinal Cord Injury

The quantification of skin resistance in individuals after spinal cord injury for the purpose of neurophysiological research is difficult, mainly as a consequence of decreased activity of sweat glands in the injured human organism. In this original work, we propose a custom electrical skin resistance transducer, featuring extremely low patient auxiliary current, linear response and high dynamic range. After the design and fabrication of the prototype device, we conducted preliminary benchmark tests. We found that our prototype transducer was able to linearly report a broad range of resistance presented to its input terminals, which is not usually found in skin resistance research instrumentation. The basic design idea is viable and, following further research, an improved version of presented prototype device may be used for the purpose of neurophysiological research in individuals after spinal cord injury.

A 96% Peak Efficiency Adaptively Controlled PSM Buck Converter With Low-Quiescent Current and Wide Dynamic Range for IoT Applications

This letter presents a fully-adaptive pulse-skip modulation (APSM) buck converter with low quiescent current and wide dynamic range for Internet of Things (IoT) systems-on-chip (SoC), which generates 0.6-1.5 V supply voltage from a battery (2.4-3.6 V). The proposed adaptive frequency modulator reduces quiescent current at no expense of transient response performance. Also, the proposed adaptive pulse-width modulator extends the dynamic range with suppressed output ripple. The chip was fabricated in 180 nm BCD process, occupying an active area of 0.56 mm. The measurement results show that the buck converter achieves 8 nA quiescent current and 10 nA to 10 mA (1×10) dynamic range. The measured peak efficiency is 96% at 3 V input voltage. A decent efficiency of 80% is also obtained even with 300 nA light load condition.

Near-Full Current Dynamic Range Thz Quantum Cascade Laser Frequency Comb

Near-Full Current Dynamic Range Thz Quantum Cascade Laser Frequency Comb

High accuracy potentiostat with wide dynamic range and linearity

Electrochemical measurement require potentiostat to ensure the operational stability during the sensing and conversion of the sensor signals. This article presents a potentiostat circuit with high linearity and accuracy bidirectional current readout circuit for a wide dynamic current range. A current conveyor circuit with a wide current range from ±50 nA to ±400 μA is constructed by combining a low-noise current mirror based OTA and a regulated current mirror employing accurate and linear output characteristics. The potentiostat is designed in 0.18 μm TSMC technology with ± 0.9 V nominal power supply, and the results obtained are based on simulation and performed with CadenceTM tools. The potentiostat circuit achieves a minimum detectable current of 1 nA within current range of ±400 μA. The detectable current range is 112 dB with R2 linearity of 0.999999993 and maximum error of 1.3%. The input referred noise of the current conveyor is 24.48 fA/Hz @1 kHz, and integrated referred noise is 0.912 pA within 0.01 Hz - 1 kHz bandwidth. The static power consumption of the potentiostat circuit is 1.993 mW. The control amplifier and the current readout circuit consume 1.98 mW and 13 μW, respectively. The proposed circuit is capable of providing low noise and high accuracy current measurement with low power consumption and highly linear output characteristics.

Improved High Dynamic Range for 3D Shape Measurement based on Saturation of the Coloured Fringe

Phase-shifting fringe projection methods have been developed for three-dimensional scanning (Zuo et al., 2018). However, the 3-Dimensional (3D) scanning of objects with a high dynamic reflectivity range based on structured light is a challenging task to achieve (Feng et al., 2018). The incorrect intensities captured will cause phase and measurement errors. Thus, this paper proposes a method that improves the current High Dynamic Range (HDR) (Jiang et al., 2016)) method to increase the dynamic range. The camera and projector have 3 channels, red, green, and blue, which can absorb and project these lights independently. This paper proposes a method that makes use of this by controlling the intensity of each projected for the camera. Each image can be split into 3 channels and provide 3 images which contain different intensities, then it will be used to compute the 3D information. In general, this is done by controlling the projection of red, green and blue (RGB) channel and apply the Jiang’s algorithm (Jiang et al., 2016). The results are compared and analysed with current HDR (Jiang’s method) and the regular three-step phase-shifting methods. From the experimental results, it has shown that our proposed method outperforms the current HDR and the regular three-step phase-shifting methods. Specifically, the proposed method manages to increase the dynamic range of the reflective property of objects. Additionally, our proposed method has also significantly reduced the times of 3D object measurements.

Terahertz single photon detectors

<p indent="0mm">Terahertz detection plays an increasingly important role in various fields, such as astronomy, national defense, security checking, and biotechnology. With the development of technology, the sensitivity of terahertz detectors is continuously improving, and the detection of terahertz single photons has been demonstrated in recent years. In the terahertz band, owing to the low photon energy of terahertz photons and serious transmission losses in the atmosphere, research and development on terahertz single-photon detectors have faced significant technical challenges. In this article, we first introduce the operating mechanisms, main performance indicators, and measurement systems for terahertz single-photon detectors and identify the basic requirements for realizing terahertz single-photon detection. We then introduce several terahertz single-photon detectors, including semiconductor quantum dot, semiconductor quantum well, and superconducting quantum capacitance detectors. The history of the development, operating mechanisms, and key indicators of these terahertz single-photon detectors is also summarized. Noise equivalent power of the order of 10⁻²¹ W/Hz^1/2 has been achieved using semiconductor quantum dot and quantum well detectors. Although both these have a large current response and dynamic range, their quantum efficiency is low. Superconducting quantum capacitance detectors have achieved single-photon detection at <sc>1.5 THz</sc> with a noise equivalent power better than 10⁻²⁰ W/Hz^1/2 and detection efficiency up to 90%. In addition, some terahertz detectors such as nanobolometers have shown potential for terahertz single-photon detection, and we introduce the operating mechanism and development status of these devices as well. We also analyze the prospects of terahertz single-photon detectors for applications in terahertz imaging, astronomical observations, and quantum information technology, highlighting some major international research projects and reported examples of such applications. We further summarize the advantages of terahertz single-photon detectors for these applications. Finally, we review the performance of terahertz single-photon detectors and discuss future development trends.

An Edge-Intelligent, Clip-on Rogowski Current Sensor With Wide Dynamic Range

Rogowski coil current sensors are popular solutions for current sensing having several advantages over current transformers (CTs), including size, bandwidth and dynamic range. These sensors have been used by electric utilities for gaining visibility into the electric grid directly helping in grid operations. This paper presents an overview of the design principles and test results for a PCB-based Rogowski coil that can be retrofitted around any existing conductor, resulting in a sensor that can be rapidly installed in the field. Due to the absence of any magnetic components in the coil, Rogowski coils cannot saturate and thus have a very high dynamic range, only limited by the accompanying signal conditioning or data converter circuits. In order to prevent saturation of the signal conditioning stage at higher current levels, a method to auto-tune the sensor has been presented, resulting in a dynamic range that is orders of magnitude higher than state of the art. The method, called dynamic range correction (DRC), uses edge intelligence to detect fault current scenarios and adjust the analog circuit to prevent saturation or distortion, while capturing the fault current waveforms. This feature enables post-event diagnostics for electric utilities at a very low cost.

Modeling and Design of FTJs as Multi-Level Low Energy Memristors for Neuromorphic Computing

An in–house modelling framework for Ferroelectric Tunnelling Junctions (FTJ) is here presented in details. After a precise calibration again experiments, the model is exploited for an insightful study of the design of FTJs as synaptic devices for neuromorphic networks. Our analysis explains and addresses the tradeoff between the reading efficiency and the effects of the depolarization field during the retention phase. The reported results show that a moderately low-κ tunnelling dielectric (e.g. SiO2) can increase the read current and the current dynamic range. The study shows also how the contribution of trapped charge may favor the stabilization of the polarization inside the FTJ, but also reduces the maximum read current.

Homogeneous quantum cascade lasers operating as terahertz frequency combs over their entire operational regime

AbstractWe report a homogeneous quantum cascade laser (QCL) emitting at terahertz (THz) frequencies, with a total spectral emission of about 0.6 THz, centered around 3.3 THz, a current density dynamic range Jdr = 1.53, and a continuous wave output power of 7 mW. The analysis of the intermode beatnote unveils that the devised laser operates as an optical frequency comb (FC) synthesizer over the whole laser operational regime, with up to 36 optically active laser modes delivering ∼200 µW of optical power per optical mode, a power level unreached so far in any THz QCL FC. A stable and narrow single beatnote, reaching a minimum linewidth of about 500 Hz, is observed over a current density range of 240 A/cm2 and even across the negative differential resistance region. We further prove that the QCL FC can be injection locked with moderate radio frequency power at the intermode beatnote frequency, covering a locking range of 1.2 MHz. The demonstration of stable FC operation, in a QCL, over the full current density dynamic range, and without any external dispersion compensation mechanism, makes our proposed homogenous THz QCL an ideal tool for metrological applications requiring mode-hop electrical tunability and a tight control of the frequency and phase jitter.

Mid-infrared frequency comb from a ring quantum cascade laser

The effect of spatial hole burning on mode proliferation has been shown both theoretically and experimentally to be important for frequency comb operation in quantum cascade lasers (QCLs). It is therefore of great interest to investigate the frequency comb operation from integrated ring cavities where this effect is absent. Here we report a mid-infrared quantum cascade laser based on a buried heterostructure ring cavity that exhibits unidirectional lasing with a frequency comb spectrum displaying a predominantly s e c h 2 profile over a bandwidth of ∼ 10 − 1 . A single beat note with 3 dB linewidth of &lt; 900 H z was observed over the last 85% of the whole current dynamic range. To further verify the frequency comb operation, a multiheterodyne experiment was carried out using a standard Fabry–Pérot QCL comb as a reference laser. This measurement allowed the retrieval of the spectral phases, indicating an operation with strong amplitude modulation.

A Microwatt Dual-Mode Electrochemical Sensing Current Readout With Current-Reducer Ramp Waveform Generation.

An electrochemical sensing chip with an integrated current-reducer pattern generator and a current-mirror based low-noise chopper-stabilization potentiostat circuit is presented. The pattern generator, utilizing the current reducer technique and pseudo resistors, creates a sub-Hz ramp signal for the cyclic voltammetric (CV) measurement without large-size passive components. The proposed design adopts the chopper-stabilization and low-noise biasing technique for the potentiostat and a counter-based time-to-digital converter to reduce the amplitude noise effects and to convert the sensing current signal to digital codes for further data processing. The design is fabricated using a 0.18-μm CMOS process and achieves a 41pA current resolution in the current range of ±5μA while maintaining the R2 linearity of 0.998. The system consumes 16μW from a 1.2V supply when a 5μA sensing current is detected. The power efficiency of the readout interface is 0.31, and the sensing current dynamic range is 108dB. The design is fully integrated into a single chip and is successfully tested in the dual-mode (CA/CV) measurements with commercial gold electrodes in a potassium ferricyanide solution in sub-millimolar concentrations.

An Extremely Low-Voltage and High-Compliance Current Mirror

In this paper, a novel ultrahigh-compliance, low-voltage and low-power current mirror is proposed. The proposed structure utilizes the cooperative positive–negative local feedback to achieve ever-interesting high output voltage compliance. The structure takes the advantage of the current compensation scheme to boost the positive feedback at high current values, in which, otherwise the positive feedback and consequently the output voltage compliance tend to be degraded. The performance of the proposed architecture is validated by HSPICE simulation in TSMC 180 nm CMOS, BSIM 3 and Level 49 technology. The simulation results of the proposed structure show input/output minimum voltages of 0.059 V/0.038 V, output resistance of 121.36 GΩ and bandwidth of 211 MHz, while it consumes only 42.5 µW considering 1 V supply voltage. The current transfer error is interestingly less than 0.4% throughout its current dynamic range.