Amplifier Circuit Research Articles

Acoustically Enhanced Triboelectric Stethoscope for Ultrasensitive Cardiac Sounds Sensing and Disease Diagnosis.

Electronic stethoscope used to detect cardiac sounds that contain essential clinical information is a primary tool for diagnosis of various cardiac disorders. However, the linear electromechanical constitutive relation makes conventional piezoelectric sensors rather ineffective to detect low-intensity, low-frequency heart acoustic signal without the assistance of complex filtering and amplification circuits. Herein, it is found that triboelectric sensor features superior advantages over piezoelectric one for microquantity sensing originated from the fast saturated constitutive characteristic. As a result, the triboelectric sensor shows ultrahigh sensitivity (1215mV Pa-1) than the piezoelectric counterpart (21mV Pa-1) in the sound pressure range of 50-80dB under the same testing condition. By designing a trumpet-shaped auscultatory cavity with a power function cross-section to achieve acoustic energy converging and impedance matching, triboelectric stethoscope delivers 36dB signal-to-noise ratio for human test (2.3 times of that for piezoelectric one). Further combining with machine learning, five cardiac states can be diagnosed at 97% accuracy. In general, the triboelectric sensor is distinctly unique in basic mechanism, provides a novel design concept for sensing micromechanical quantities, and presents significant potential for application in cardiac sounds sensing and disease diagnosis.

Time-resolved synchrotron light source X-ray detection with Low-Gain Avalanche Diodes

Low Gain Avalanche Diodes (LGADs) represent the state-of-the-art in timing measurements and will instrument future timing detectors at the High Luminosity Large Hadron Collider (HL-LHC) experiments. While conceived as a sensor for charged particles, the intrinsic gain of LGADs makes it possible to detect low energy X-rays with good energy resolution and excellent timing (tens of picoseconds). Using the Stanford Synchrotron Radiation Lightsource (SSRL) at SLAC, several LGADs designs were characterized with energies from 5 to 35 keV. The SSRL provides 10 ps pulsed X-ray bunches separated by 2.1ns intervals, and with an energy dispersion (ΔE/E) of 1 × 10-4. LGADs fabricated by Hamamatsu Photonics (HPK) and Brookhaven National Laboratory (BNL) with different thicknesses ranging from 20µm to 50µm and different gain layer designs were read out a two stage fast amplification circuit and digitized with a high bandwidth, high sampling rate oscilloscope. PIN devices from HPK were characterized as well. A systematic and detailed characterization of the devices’ energy linearity, resolution and timing resolution as a function of X-ray energy was performed for different biasing voltages at room temperature.

Automatic in-situ measurement of thermal resistance for GaN HEMTs

An automatic in-situ technique for thermal resistance measurement based on an electrical method is proposed in this paper. In contrast to the conventional thermal resistance measurement circuits of the electrical method, this method involves direct measurement of the thermal resistance of GaN high-electron-mobility transistor (HEMT) devices in an operating circuit by introducing a well-matched radio-frequency switching circuit into the operating circuit. The advantage of this method is that the thermal resistance can be measured periodically on the in-situ device without changing the electrical characteristics of the device. Based on this result, the cooling curve of the HEMT device in the power amplifier (PA) circuit is collected and the thermal resistance characteristics of the HEMT are determined via the structure function method. The purpose of this paper is to successfully obtain the thermal resistance of in-situ devices through an automatic in-situ measurement circuit of thermal resistance, and to verify the feasibility of periodic detection of thermal resistance of in-situ devices.

A phased array ultrasonic transducer linear sinusoidal driving system for ultrasound neuromodulation

Ultrasound application has been proven to be a promising noninvasive neuromodulation technique due to the high penetration depth, and high focusing properties. Compared to single-element ultrasonic transducers, phased array transducers have the advantages of adjustable focusing targets and higher focusing accuracy, making them more suitable for transcranial neuromodulation technology. However, there is currently limited research on phased array ultrasonic transducer linear sinusoidal driving systems for precise transcranial neuromodulation. This paper develops a new type of phased array linear driving system, using sine wave as input wave, and designs a new OCL-AB power amplifier circuit based on the Output CapitorLess circuit (OCL) and Class-AB circuit. Furthermore, the dedicated input signal generator and focusing control module are designed and combined with the excitation circuit to form a balanced transformerless (BTL) structure to further boost the output voltage. The experimental results show that the 16-channel prototype of the system can meet various parameter requirements for neural regulation under standard mode ±60 V and BTL mode ±120 V output voltage at 100KHz-1 MHz, and has smaller focusing spot and higher frequency accuracy.

Non-invasive Blood Glucose Monitoring System

The project presents a novel approach to blood glucose monitoring, offering a non-invasive and pain-free method for individuals with diabetes to track their glucose levels. The system utilizes advanced sensor technology coupled with signal processing techniques to detect glucose levels in the body without the need for traditional needle pricking. The key components of the system include a power supply, voltage regulator, ESP32 microcontroller, LCD display, photo sensor, amplifier circuit, and linearization circuit, all seamlessly integrated to provide accurate and real-time glucose readings. This breakthrough technology holds great promise in revolutionizing diabetes management, enhancing the quality of life for millions of affected individuals.By placing the sensor on the individual’s hand, the Glucometer system employs a combination of photonic and electronic principles to non-invasively measure glucose levels. The photo sensor captures specific wavelengths of light that interact with glucose molecules within the tissue, generating a signal proportional to the glucose concentration. This signal is then amplified and processed through the integrated circuits, ensuring accurate linearization and calibration. The ESP32 microcontroller orchestrates these operations, facilitating seamless communication with the LCD display to present the glucose reading in a clear and user-friendly format.The Glucometer’s innovative design eliminates the discomfort associated with traditional blood sampling methods, making it a highly accessible and convenient tool for diabetes management. The system’s efficiency in providing accurate glucose readings without the need for invasive procedures represents a significant advancement in healthcare technology. With further development and refinement, the Glucometer holds the potential to significantly enhance the daily lives of individuals living with diabetes, offering a reliable and painless means of monitoring blood glucose levels.

An Inductance-Capacitance Measurement Method Based On Auto-Balancing Bridge

Modern measurement modules are extremely demanding on the hardware and must accurately capture the relevant parameters of capacitance and inductance. The inductance and its quality factor, capacitance and its loss angle tangent value are very important parameters, but also the current testing difficulties. To efficiently and accurately measure the inductance and its quality factor, capacitance and its loss angle tangent, this paper developed a capacitance-inductance testing method based on automatic balanced bridge circuit. Firstly, based on the DSP development board, test capacitance and inductance by switching dip switches; Then, the use of self-excited oscillation method to generate a fixed frequency sinusoidal signal, through the amplifier to increase the amplitude of its signal, and the use of adder to the signal to provide a certain bias to meet the amplitude requirements; Finally, based on the automatic balanced bridge method, through the full-wave rectification plus filter will be converted into the average of the signal to be tested, and then use the amplifier circuit to control the average value of the signal to be tested, and then use the amplifier circuit to control the average value. Then use the amplifier circuit to control the average value within the AD sampling range, and use the micro-controller to collect the test amplitude, phase and other related parameters. The test results show the effectiveness of the proposed method.

A Precision Measurement System Design for Electrical Conductivity in the Low-Concentration TOC Analysis of the Ultra-pure Water

The concentration of total organic carbon (TOC) in water is an important key indicator of the quality of Ultra-pure water, which is useful in the semiconductor and pharmaceutical industries, among others. Therefore, as a technology to measure TOC, a technology that measures the amount of carbon dioxide (CO<sub>2</sub>) by electrical conductivity is being developed. This method uses ultraviolet light and an oxidizing agent to oxidize organic compounds to produce CO<sub>2</sub>, and measures the concentration of CO<sub>2</sub> by measuring the electrical conductivity based on the permeable membrane of the gas, and then converts it to the concentration of TOC in the organic compound. In this study, we presented the design conditions of the alternating current control circuit applied between the two electrodes of the electrical conductivity cell, the microcurrent signal detection, voltage conversion circuit, and the amplification and noise reduction circuit for measuring the low concentration of TOC required for ultrapure water. Based on the optimal design conditions, we have fabricated a PCB for ultra-precise electrical conductivity measurement for low concentration TOC analysis using membrane conductivity, and have compared the results with a commercial product.

Development of an Electronic Photo Sensor for Chlorophyll Detection

The amount of chlorophyll in plant leaves can be measured using time-consuming and challenging traditional chemical procedures; alternatively, highly expensive sensor-based meters are available in the market. In this paper, the design of an inexpensive, less complex, optimum-sized ESP-32-based electronic chlorophyll reader is presented. For the suggested electronic reader the design of the photosensor circuit is the primary focus of the study. It includes designing current amplifier circuits for photodetectors and LED driver circuits for red and infrared LEDs. Spectral absorption by leaf chlorophyll is the parameter used for measuring chlorophyll. Regarding leaf chlorophyll spectral absorption, red LEDs are the most absorbing. Utilizing this function, red LED spectrum absorption measurements are made for various plant leaves. The chlorophyll content of the same leaves is then determined in the botany lab using Arnon's method. To confirm the photosensor design, the red LED spectrum absorbance and the chlorophyll identified using Arnon's technique are analyzed for different leaves. The photosensor is verified to be operating correctly. Additionally, a linear regression model for performance analysis is provided.

Design and Testing of a Fast-Response Preamplifier

This article presents the design of a high-speed, low-noise preamplifier specifically intended for amplifying high-frequency weak electrical signals. Firstly, a thorough analysis was conducted on common types of preamplifiers, and it was proposed to adopt a charge-sensitive preamplifier as a solution for signal output amplification. Subsequently, a specific circuit was carefully designed and thoroughly analyzed to ensure it meets the strict requirements of low noise and nanosecond-level response. To verify the feasibility of the designed amplification circuit, an actual circuit board was fabricated and electronic tests were conducted. The test results revealed that the electronic noise of the amplifier was only 5mV, and the signal response time was within 5ns, fully demonstrating its excellent performance.

A Real-Time Monitoring Method for Selective Laser Melting of TA1 Materials Based on Radiation Detection of a Molten Pool.

Selective laser melting (SLM) technology is a promising additive manufacturing technology. However, due to the numerous influencing factors in this complex process, a reliable real-time method is needed to monitor the forming process of SLM. The molten pool is the smallest forming unit in the SLM process, the consistency of which can effectively reflect the quality of the printing process. By using a coaxial optical path structure and a compound amplifier circuit, high-speed acquisition of molten pool radiation can be realized. Next, single factor analysis and orthogonal experimentation were used to investigate the influence levels of key process parameters on the radiation of molten pool. In addition, numerical simulation was carried out with the same parameter setting schemes, the results of which are consistent with those in radiation detection experiments. It is shown that the laser power has the greatest effect on the radiation of the molten pool, while the scanning speed and the hatch spacing have little effect on the radiation. Finally, the positioning experiment involving the small hole structure was carried out, and the experimental results showed that the device could accurately locate the position coordinates of the given hole structure.

Architecture-level energy model for high-capacity STT-MRAM memory

ABSTRACT Nowadays, STT-MRAM has emerged as one of the leading contenders for next-generation memory technologies. However, STT-MRAM still exhibits high energy consumption due to its peripheral circuits, including the read/write and the sample amplifier (SA) circuits. Therefore, it is crucial to accurately evaluate the energy consumption of memory architectures during the early stages of the design process. Traditionally, energy evaluation can be conducted using the NVSim platform. However, the peripheral read/write circuitry of STT-MRAM undergoes iterative improvements, which cannot be promptly incorporated into NVSim. To addreGss this limitation and to enable comprehensive energy consumption evaluations spanning from device-level to architecture-level for STT-MRAM, an architecture-level energy consumption model is proposed in this paper. The model offers high accuracy and flexibility for the STT-MRAM memory array structure, abstracting the influences of read/write circuits for power evaluations. Comparative analysis is performed between the proposed model and the traditional approaches. When estimating a memory array with 128 × 64, the deviation using the proposed model is less than 2%, showing improved accuracy compared to that with analytical formulas. Notably, the proposed model offers up to 97% time savings in the whole circuit simulation, thus enhancing efficiency in the design and evaluation process.

RESEARCH OF STRUCTURAL AND MECHANICAL PROPERTIES OF MEAT AS AN OBJECT OF PROCESSING IN MEAT COMMINUTOR

Reliable assessments of the state of modern energy show the relevance of scientific and technical developments aimed at solving its problems. In this regard, the use of resonance phenomena in electrical circuits with active-reactive elements acquires particular significance. Their various combinations open up exceptional opportunities for creating fundamentally new efficient energy sources. This article discusses a resonant active electrical power amplifier containing a sequence of several electrically connected active-reactive circuits, which, depending on the purpose, are excited in the voltage resonance or current resonance mode. An equivalent circuit is proposed for the proposed resonant amplifier of active electrical power, represented by two blocks, each of which consists of a sequence of inductively coupled active-reactive circuits excited at the same frequency. Calculations are presented showing the theoretical justification for the performance of the proposed scheme. The analysis of ongoing electromagnetic processes was carried out using well-known methods of the theory of electrical circuits without involving any hypotheses about the physics of resonance phenomena. It is shown that in the proposed amplifier circuit, the first block amplifies the reactive power of the harmonic signal with a high conversion coefficient, the second, with a slight gain, converts the reactive power of the harmonic signal into active power. The results of calculations are presented, illustrating the functional dependence of the integral gain on the main characteristics of the output resonant circuit. Numerical estimates of the main characteristics of the proposed circuit showed that with an appropriate choice of its parameters, high values of the output characteristics are possible, so the gain can reach a value of ~ 48. The significance of the results obtained for practice lies in their use for formulating recommendations for the creation of real efficient sources of electrical energy, the principle whose actions are based on the use of natural resonance phenomena.

Design and Analysis of Micro Signal Detection Circuit for Magnetic Field Detection Utilizing Coil Sensors

Eddy current inspection has been extensively employed in non-destructive testing of various conductive materials. The coil probe, as a mainstream sensor in the eddy current detection system, inevitably encounters interference from external signals while transmitting its own signal. Therefore, developing techniques to extract valuable signals from noisy ones is crucial for ensuring accurate detection. Carbon fiber composites not only possess significantly lower electrical conductivity compared to conventional metallic materials but also exhibit notable anisotropy. To address this issue, we designed an ‘8’ coil probe set where the excitation coil does not electromagnetically interfere with the detection coil. However, practical applications that require portability and miniaturization pose challenges when utilizing this coil probe set to identify carbon content or defects due to the typically weak output signal. To address this issue, this paper proposes a design that combines the ‘8’ structure of the planar coil probe with the principle of phase-locked amplification to create a dual-phase sensitive phase-locked amplification detection circuit. These specific design ideas were tested using a weak signal, which passed through the preamplifier, secondary amplifier, and band-pass filter comprising the target channel for signal amplification and noise filtering. The effective signal amplitude is proportional to the inverse phase difference between the direct current (DC) signal and inversely proportional to the amplitude of the signal. Finally, the DC signal was passed through an analog-to-digital converter (ADC). The analog-to-digital converter (A/D) is used to collect and calculate the DC signal, enabling the detection of weak electrical signals. Simulation experiments demonstrated that the signal detection circuit has an amplitude error below 0.2% and a phase error below 0.5%. The phase-locked amplification circuit designed in this paper can effectively extract the tiny impedance change signals of the planar coil sensor probe with high sensitivity and good robustness.

A NOVEL APPROACH OF NON-DESTRUCTIVE TESTING FOR W-BEAM GUARDRAIL DEFECT DETECTION USING SURFACE WAVE TECHNOLOGY

The W-beam guardrail, alternatively referred to as a guardrail or railing, constitutes a system meticulously engineered to prevent vehicular deviation into hazardous or restricted zones. Such mechanisms are ubiquitously employed across major global thoroughfares. However, vehicular collisions can inflict considerable damage upon the W-beam, thereby compromising its structural integrity. Concurrently, subpar maintenance further exacerbates this issue, potentially transforming the W-beam from an accident prevention tool into a catalyst for mishaps. Hence, the implementation of an effective maintenance and inspection strategy is imperative. The research presented herein proposes a novel method for W-beam defect detection, leveraging surface wave technology. A pulse-echo setup has been established, employing a 10-cycle tone burst to operate at a centre frequency of 48 kHz as the transmission medium. Signals reflected from the defective specimen were subsequently analysed; however, it was observed that this technique was unable to detect all defects. Despite these limitations, the study delineates the potential to pinpoint the precise location of physical hole defects. This was achieved through the time-of-flight method and leveraging known material characteristics, such as the speed of sound, at 5 cm between the hole and transmitter. The researchers predict that this methodology, when augmented with a higher voltage and a suitable amplifier circuit for detection, could be utilized for long-distance defect detection. This opens up new avenues for ensuring the structural integrity of W-beam guardrails, thereby enhancing road safety.

Hardware Implementation of a Fully Functional Stochastic p‐STT Neuron for Probabilistic Computing

AbstractA stochastic binary neuron is developed for probabilistic computing using a perpendicular spin‐transfer torque (p‐STT) neuron device and its associated peripheral circuits. The p‐STT neuron device, featuring a 300‐nm‐diameter pillar structure and a perpendicular magnetic‐tunnelling‐junction spin valve, is fabricated to exhibit stochastic switching behavior characterized by a sigmoidal function. The stochastic switching mechanism is influenced by the presence of defect sites within the device. The hardware implementation encompasses the construction of the neuron peripheral circuit, including the fire‐spike generation, sensing amplifier, and reset circuit, using a 28‐nm‐design‐rule complementary metal‐oxide‐semiconductor (C‐MOSFET) process. This hardware realization also demonstrates stochastic switching behavior with a sigmoidal function. However, a slight shift toward higher input voltage spike amplitudes is observed compared to the p‐STT neuron device alone, owing to voltage drop within the peripheral circuit. Furthermore, the software‐based investigation focuses on validating the feasibility of a spiking neural network. The temporal correlation detection is estimated using the stochastic switching probability derived from the hardware implementation, indicating successful synchronization between the correlated input neuron and the output p‐STT neuron.

Comparison of Magnetostrictive-Actuated Semi-Active Control Methods Based on Synchronized Switching

Three distinct synchronized switching circuits based on a magnetostrictive actuator are compared in this paper to examine their control mechanisms and circuit characteristics. These circuits include a semi-active shunt circuit, a semi-active current inversion and amplification circuit, and a semi-active automatic current inversion and amplification circuit. Each circuit type employs an additional electronic switch. The synchronized switching method enables the rational control of the circuit current generated by the magnetostrictive actuator to fulfill any desired control strategy. Simulation and experimental results on a 10-bay truss structure reveal that the three circuits can effectively adjust the polarity of the induced current as needed. The three circuits are then compared to thoroughly analyze their unique characteristics and explain their respective advantages and dis-advantages. Using the comparison results, various options available for control circuit design are demonstrated.

Lead ions detection using CVD-grown ReS2-FET with the facilitation of a passivation layer

Field-effect transistor (FET)-based heavy-metal detection is garnering attention due to its heightened sensitivity, affordability, convenient fabrication, and portability. Flower-like rhenium disulfide (ReS2) offers potential for high-performance FET sensors, but direct exposure of channel materials to the ionic solution without a passivation layer results in multiple signals arising from the ionic transmission, doping impact, and gating effect. Introducing a passivation layer to the channel surface enhances sensor sensitivity without compromising device performance, ensuring conductance changes are primarily due to the gating effect. Here, a large surface area of Chemical Vapor Deposition (CVD)-grown vertically aligned ReS2 is employed in the FET-based sensor, and the utilization of the HfO2 layer is to isolate analytes from the elements of the conducting channel. For real-time lead monitoring in a water environment, it exhibits strong electrical stability, an impressive LoD (≈2 nM), a rapid response time (≈1.1 sec), and notable selectivity. Additionally, sensing operations are characterized by developing a unique amplifier circuit by integrating the fabricated sensor, contributing to advancements in sensor integration to detect hazardous metals in industrial electronics. These results underscore the potential for enhancing the performance of ion-sensitive FETs through structural optimization and improvements to the fundamental sensor mechanism.

Unleashing Endurance Limits of Emerging Memory: Multi-Level FeRAM Recovery Array Empowered by a Coordinated Inverting Amplifier Circuit

Unleashing Endurance Limits of Emerging Memory: Multi-Level FeRAM Recovery Array Empowered by a Coordinated Inverting Amplifier Circuit

Enhancing Preamplifier Design for Acoustic Emission Detection Instrument

With the development of the industry, the safety of pressure vessels is crucial for both production and personnel safety. The application of acoustic emission testing technology as a dynamic non-destructive testing method in the detection of pressure vessels is becoming increasingly prevalent. This paper presents the design of a low-frequency acoustic emission preamplifier with a frequency range of 30KHz to 200KHz and a gain of 20dB. The preamplifier is composed of amplification circuits, power supply circuits, and filtering components. By utilizing the PXR04 series high-sensitivity resonant acoustic emission sensor and Texas Instruments' OPA333 operational amplifier, along with a clever power supply design, effective signal amplification and system stability are ensured. Experimental results validate the correctness of the design, providing a feasible and effective solution for enhancing the performance of acoustic emission testing equipment.

Complementary integration of organic electrochemical transistors for front-end amplifier circuits of flexible neural implants.

The ability to amplify, translate, and process small ionic potential fluctuations of neural processes directly at the recording site is essential to improve the performance of neural implants. Organic front-end analog electronics are ideal for this application, allowing for minimally invasive amplifiers owing to their tissue-like mechanical properties. Here, we demonstrate fully organic complementary circuits by pairing depletion- and enhancement-mode p- and n-type organic electrochemical transistors (OECTs). With precise geometry tuning and a vertical device architecture, we achieve overlapping output characteristics and integrate them into amplifiers with single neuronal dimensions (20 micrometers). Amplifiers with combined p- and n-OECTs result in voltage-to-voltage amplification with a gain of >30 decibels. We also leverage depletion and enhancement-mode p-OECTs with matching characteristics to demonstrate a differential recording capability with high common mode rejection rate (>60 decibels). Integrating OECT-based front-end amplifiers into a flexible shank form factor enables single-neuron recording in the mouse cortex with on-site filtering and amplification.