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This article presents a circuit model that is able to capture the full nonlinear behavior of an asymmetric electrostatic transducer whose dynamics are governed by a single degree of freedom. Effects such as stress-stiffening and pull-in are accounted for. The simulation of a displacement-dependent capacitor and a nonlinear spring is accomplished with arbitrary behavioral sources, which are a standard component of circuit simulators. As an application example, the parameters of the model were fitted to emulate the behavior of an electrostatic MEMS loudspeaker whose finite-element (FEM) simulations and acoustic characterisation where already reported in the literature. The obtained waveforms show good agreement with the amplitude and distortion that was reported both in the transient FEM simulations and in the experimental measurements. This model is also used to predict the performance of this device as a microphone, coupling it to a two-stage charge amplifier. Additional complex behaviors can be introduced to this network model if it is required.

The charge-generating sensors are widely used in many applications in consumer, automotive and medical electronics. They generate a charge proportional to the applied input quantity: pressure, temperature, acceleration, strain, light, etc. Usually, charge amplifiers are used to register such signals. The charge amplifier is an integrator that integrates the input current over time. In continuous-time signal processing, a parallel resistor is used to dissipate the energy stored on the integration capacitor, and such self-zeroed integrator circuits are known as lossy integrators. To achieve low-frequency operation, when a capacitor is in the picofarad range, a very high-ohmic resistor, in the range of gigaohms, must be used. Such a high-ohmic resistor increases the output offset voltage to an unacceptable level. To overcome the output offset problems, a composite charge amplifier has been recently introduced. This paper presents an innovative lossy integrator readout circuit which contains only one opamp in the feedback. The circuit can be easily adapted to the needed gain and cut-off frequency. Its operation is validated by experimental results. The sufficiently low high-pass cut-off frequency allows the circuit to be used for biosignal amplification. Heart and respiration rates can be easily recorded with piezoelectric sensors attached to the wrist or lung wall. The presented circuit can benefit many applications where charge-to-voltage conversion is needed.

This paper presents a ScAlN/AlN-based MEMS piezoelectric accelerometer using the trapezoidal with corners (TWC) shaped cantilevers. The composite Sc0.2Al0.8N/AlN piezoelectric film is deposited on a silicon-on-insulator (SOI) substrate to improve the sensitivity of the piezoelectric accelerometer. The theoretical and FEM model is established to analyze the relationship between the cantilever stiffness and the piezoelectric parameters on the sensitivity and resonance frequency. The fabricated accelerometer includes a trapezoidal part, a rectangular part, and a silicon proof mass. The experimental results show that the sensitivity, minimum detectable signal (MDS), resolution, and resonant frequency of the proposed TWC shaped accelerometer are 7.95 mV/g, 1 mg, 1 mg, and 1290 Hz, respectively. The manufactured accelerometer exhibits good linearity up to 2 g (non-linearity ${T}=300$ K), the thermal noise of the fabricated accelerometer is lower than 94.7 nV/ $\surd $ Hz. Meanwhile, the charge amplifier circuit noise is about $1.97~\mu \text{V}/\surd $ Hz. The proposed TWC accelerometer is sensitive and suitable to sense vibration acceleration in low-frequency scenarios.

Non-contact capacitive electrodes are very suitable for wearable devices to acquire electrophysiological signals in an unobtrusive and long-term way. However, due to its poorly-defined and low electrode capacitance (Ce), its front-end amplifier requires a large biasing resistance (e.g., > 100 GΩ) to maintain a sub-Hz high-pass frequency and low circuit noise. This paper compares two amplifier structures, i.e., a voltage amplifier (VA) and a charge amplifier (CA), each with three biasing strategies, i.e., pseudo resistors, switched resistors and reset switches. These, in total six, amplifier designs were fabricated in a standard 180nm CMOS technology and compared in terms of their input impedance, transfer function and input-referred noise. As final result, the VA and CA structures have comparable performance. In terms of biasing network, the pseudo resistor can achieve hundreds of GΩ, the switched-resistor only reaches several GΩ due to parasitics, and the reset switch achieves a TΩ resistance when it is shut off, and therefore results in the lowest high-pass frequency and the best noise performance.

Objective: Sensing with capacitive electrodes is of interest for long-term, comfortable bio-potential measurements (e.g., ECG). However, due to the small body-to-electrode capacitance (C e ), the design of the associated front-end amplifier remains a challenge. Both voltage amplifiers (VA) and charge amplifiers (CA) can be employed. While basic comparisons of both typologies were done before, this paper extends the comparison to their responses to artifacts (caused by motion or interference). Further, a VA-CA-switchable amplifier is proposed, allowing to adapt the amplifier type to different situations, and enabling to estimate the body-to-electrode capacitance C e in a passive way. Methods: A VA-CA switchable amplifier was implemented in a 180 nm CMOS process. The responses to artifacts for VA and CA were studied by modelling, simulations and experiments using the custom IC. The proposed C e estimation method was validated by electrical tests and in-vivo tests. Results: VAs are less affected by C e variation artifacts, while CAs recover faster from triboelectricity artifacts. In a VA, these two artifacts are multiplicative and get modulated if they occur simultaneously, but in a CA they remain independent. Conclusion: The combined VA-CA amplifier has the potential for optimal amplifier selection according to the properties of the recorded signal, the value of C e and the actual presence of artifacts. Moreover, it can estimate C e without extra hardware. Significance: The proposed VA-CA switchable structure is superior to an individual VA or CA, thanks its adaptability to signal quality and artifacts, and it provides extra information on the body-to-electrode interface quality (C e ).

Liquid xenon time projection chamber (LXe TPC) is widely used in high-energy physics experiments such as particle detection and neutrino (or neutrinoless) double beta decay. The charge readout accuracy of the LXe TPC directly affects the measurement results and success of the experiments. Because liquid xenon needs to maintain a cryogenic temperature between 162 and 165 K at atmospheric pressure, the charge generated in the LXe TPC always needs to be read out in the cryogenic environment for minimizing the input capacitance, which has effect in determining the output noise of the charge amplifier. Design a charge readout electronics system applicable to LXe TPC and research a data analysis method to get the exact amount of charge by analyzing the waveform at that output of the designed electronics system. Design a multi-channel charge-reading application specific integrated circuit (ASIC) that can operate in the cryogenic environment. The signals and power supply of the ASIC are connected to an electronics system at room temperature through micro-coaxial cables. The electronics at room temperature complete the sampling of the ASIC output. A data acquisition device receives the sampled waveform data and calculates the charge measurement resolution by Gaussian fitting. The designed ASIC and selected micro-coaxial cable can work in stable condition under the cryogenic environment of 165 K. The analyzed integral nonlinearity of the charge measurement of the chip is 0.83% in the range from 1 to 50 fC, and the charge measurement resolution of the chip is lower than 900 $$\hbox {e}^-$$ RMS. In this paper, a preliminary study of the charge readout method based on the system structure of self-developed ASIC, micro-coaxial cable, and data readout electronics is completed for LXe TPC. The system test results indicate that the designed ASIC can work normally in the cryogenic temperature of 165 K with a high dynamic range and good linearity of the charge measurement. Further work can be done to reduce the charge measurement resolution of the system to 200 $$\hbox {e}^-$$ RMS.

Piezo-electric sensors have found widespread application today due to their ability to provide an interface between the mechanical and electronic world. For humans, in order to interact with these materials, we require an electronic interface. This paper describes one of the possible interfaces, which includes a charge amplifier cascaded with a filter circuit to obtain the frequency response. A novel circuitry consisting of a rectifier and comparator is used to identify the activated channels of the array of piezoelectric sensor. This signal conditioning circuit makes use of active devices such as op amps and nonlinear devices such as diodes along with passive components. The novel circuitry is designed for 2 channels, and demonstrates the logic of selection of these based on the signal parameters. This concept can be extended to any number of channels.

We have developed a real-time dose monitoring system for a low-energy ion-beam facility. Before we developed the monitoring system, the system had given a substantial error of ±23% when we irradiated an ion beam with a dose as much as 3.0 × 1016 cm−2 on the Si substrate. Moreover, a low irradiation dose as small as 1013 cm−2 was scarcely able to be controlled because of a too short irradiation time of several seconds, producing a greater dose error. To develop a real-time dose monitoring system, in this work, we employed a current integrator in conjunction with a beam stopper, by which a dose of 3.0 ×1016 cm−2 can be exactly irradiated on the sample with less than ±6% error, which was ensured by the measurements of Rutherford backscattering spectroscopy.

The circuit structure and the experimental performance of a newly integrated multichannel charge-sensitive preamplifier for silicon or germanium detectors are shown. The circuit has been conceived and optimized for the silicon detector GAL-TRACE, employed for light and heavy ion spectroscopy in nuclear physics experiments. The chip includes four channels optimized for anodic signals and one channel specifically designed for cathodic signals. An I2C interface is used to adjust, as needed, a host of key parameters of the preamplifier, such as sensitivity and bandwidth. An integrated range booster yields an exceptional dynamic range of 103 dB for the cathodic channel. The circuit features a low power consumption of 11 mW per channel, a fast rise time of the order of 10 ns, and low noise. Thanks to an accurate design of the input stage, the equivalent noise charge, measured with a commercial shaping amplifier, is as low as 130 rms electrons at a shaping time of 6 $\mu \text{s}$ with 5 pF of detector capacitance. The bandwidth of the preampifier is adequate for pulse shape analysis techniques used for particle discrimination.

In this study, we examine the feasibility of designing a MEMS microphone employing a levitation based electrode configuration. This electrode scheme enables capacitive MEMS sensors that could work for large bias voltages without pull-in failure. Our experiments and simulations indicate that it is possible to create robust sensors properly working at high DC voltages, which is not feasible for most of the conventional parallel plate electrode-based-microscale devices. In addition, the use of larger bias voltages will improve signal-to-noise ratios in MEMS sensors because it increases the signal relative to the noise in read-out circuits. This study presents the design, fabrication, and testing of a capacitive microphone, which is made of approximately 2 μm thick highly-doped polysilicon as a diaphragm. It has approximately 1 mm 2 surface area and incorporates interdigitated sensing electrodes on three of its sides. Right underneath these moving electrodes, there are fixed fingers being held at the same voltage potential as the moving electrodes and separated from them with a 2 μm thick air gap. The electronic output is obtained using a charge amplifier. Measured results obtained on three different microphone chips using bias voltages up to 200 volts indicate that pull-in failure is completely avoided. The sensitivity of this initial design was measured to be 16.1 mV/Pa at 200 V bias voltage, and the bandwidth was from 100 Hz to 4.9 kHz.

A low-power ultrasonic communication system conceived for cargo container monitoring is presented. Two piezoelectric transducers operating at 40 kHz are used for generating and acquiring an ultrasonic signal through the metallic wall, thus establishing a non-invasive inside-outside communication that preserves the container integrity. Both transducers are fixed by means of a novel magnetic case designed for optimizing data transmission. The acoustic and electrical characteristics of the ultrasonic channel are analyzed. An experimental measurement setup based on FPGA has been implemented for comparing some basic modulation and detection schemes in terms of Bit Error Rate (BER), also considering their robustness against undesired mechanical and electromagnetic perturbations. On this basis, a compact digital DBPSK modulator using a square carrier signal is proposed. Frequency and amplitude tracking algorithms are designed for optimizing the quality and robustness of the data transmission. Finally, a low-power low-rate (up to few kbps) architecture based on the previous elements is presented. All the proposed contributions are experimentally validated. This work was supported in part by Spanish Agencia Estatal de Investigación and Fondo Europeo de Desarrollo Regional under Grant TEC2016-80396-C2-1-R, and in part by the Obra Social La Caixa, Fundación Caja Navarra (Convocatoria 2018 de Captación de Talento).

The charge amplifier is an important building block in various electronic circuits. In this paper a new charge amplifier for piezoelectric sensors is introduced. The advantages of the new proposed charge amplifier becomes obvious in the quasi-static applications. In some quasi-static applications the traditional charge amplifiers uses an extremely large feedback resistor (in the range of $\text{G}\Omega $ ) whereas the proposed charge amplifier no longer requires such extremely large resistors. Moreover the proposed circuit reduces the output offset voltage significantly in comparison with conventional charge amplifier. The proposed circuit can be also implemented by using general purpose JFET operational amplifiers instead of using electrometer operational amplifiers therefore the cost of implementation will be reduced significantly in comparison with conventional charge amplifier. The proposed charge amplifier was assembled by using general purpose JFET Op-Amp to capture and amplify the output voltage of the piezoelectric vibration sensor Minisense100. In this experiment the low-cutoff frequency and the gain of the proposed charge amplifier were set equal to 0.2Hz and 20.5 dB respectively. The output offset voltage of the circuit was measured equal to 210 $\mu \text{V}$ .The measurement of very small vibration (±0.015g) showed a relative error equal to 2.1% with respect to the value which is obtained by using vibration meter as reference.

We present the fabrication and characterization of an array of microbridge-structured magnetoelectric (ME) thin film sensors which are constructed by an ME composite consisting of a 1 $\mu \text{m}$ PZT film and a 1 $\mu \text{m}$ amorphous FeCoSiB film deposited on a partially thinned Si substrate. Characterization of the sensor showed a large ME coefficient of $16.87~\text {V/cm}\cdot \text {Oe}$ in resonance at 7.9 kHz without a charge amplifier. The sensitivity was enhanced by 1.65 times when three identical sensors were connected in series. The resonant frequency of the sensor was precisely regulated by adjusting the etched area of the substrate, and the 3 dB bandwidth of the resonant frequency was doubled after two adjusted sensors were connected in parallel.

Parameters such as capacitance and conductivity are measured to describe the properties of a medium, including its moisture content. These methods do not deliver highly accurate results in materials that are characterized by low homogeneity, varied porosity, high conductivity and high water content. This study proposes a more accurate method for estimating the parameters of any medium. In the experimental setup, a charge amplifier and a phase-sensitive voltmeter were applied to determine resistance and capacitance parameters of a medium based on the signals received by the measuring system. The proposed method can be applied to non-homogeneous media containing both dielectric and conductive materials. The described measuring system is composed of two flat electrodes whose size can be adapted to the dimensions of the analyzed medium. A method for processing the sensing signal to determine the impedance characteristics of a medium with the use of a phase-sensitive voltmeter was described. The measuring system was modeled in Matlab/Simulink, and the results were discussed.

The piezoelectric sensors are the main electronic devices widely used to measure the instantaneous force that is exerted on the sensor surface by vehicle wheels moving at normal speed. This application is typically implemented in High Speed Weigh in Motion system, which has been until today under research studies. The system aims to perform an accurate and reliable axle load measurement of heavy trucks in motion. The piezoelectric sensor produces a voltage when a strain is applied on its surface. In general, the voltage signal is in a pulse form as a deterministic signal, easy to operate, but often it is not so. This problem is due to more signal noise, for the most part, because of either the modest quality of piezoelectric sensor or the inefficiency of sensor signal conditioning stage design. The present paper introduces a newly readout system allowing the processing of the piezoelectric sensor output signal in response of exerted force. The studied system consists on the charge amplifier, which is coupled with a transistor used in decoupled common emitter. This circuitry scheme cancels noise and random effect on sensor signal. The purpose of the present study focuses on the achievement of a reliable and deterministic signal, using a sensor with modest quality. The experiment results show the efficiency of the proposed readout system. Even though more noises affect the piezoelectric sensor output signal, the proposed electric interface provides a deterministic and suitable analog signal offering more possibilities to process with the standard tools of signal processing.

In-line measurement of the mass flow rate of solids in pneumatic conveying pipelines is essential for the efficient and optimized operation of many industrial processes. This paper presents a comparative study of using induced and transferred charges from non-intrusive electrodes exposed to the particle flow for mass flow rate measurement. A novel signal conditioning circuit, which consists of a current sense amplifier and a charge amplifier, is designed to convert the induced and transferred charges into two separate voltage signals. Empirical measurement models that relate the particle velocity, the root-mean-square (r.m.s) magnitude of the induced charge signal and the slope of the transferred charge signal to the mass flow rate are proposed. Experiments were undertaken using electrodes of different widths and under different mass flow rate and particle velocity conditions. Results obtained show that both the r.m.s magnitude of the induced charge signal and the slope of the transferred charge signal increase with the mass flow rate and the velocity of particles. In general, the measurement results using the induced and transferred charges from either the narrow or the wide electrode are similar. However, the method based on the transferred charge is less reliable due to confined sensing area and electrode charging by particles adhered to the electrode surface.

In this paper, a low noise and low power analog front end for piezoelectric microphones used in hearing aid devices is presented. It consists of a Charge Amplifier, followed by a Variable Gain Amplifier and an Analog-to-Digital Converter. At the core of charge amplifier a two stage opamp with modified cascode current mirror is designed which achieves a gain of 93 dB and phase margin of 62°. Designed analog front end achieves an input referred noise of 0.12 μVrms and SNR of 74 dB. It consumes power of 430 μW from 1.8 V supply and occupies an area of 1.2 mm × 0.22 mm. Proposed circuit is designed and fabricated in 0.18 μm CMOS process. Designed circuit is interfaced with a sensor model of piezoelectric microphone, which mimics Ormia ochracea's auditory system, and its performance is successfully verified against simulation results.

A charge amplifier with noise peaking suppression and gain drop compensation is proposed. By utilizing the proposed Quasi-Miller RC network, the noise peaking is suppressed and gain drop is compensated, which alleviates the design trade-off between charge gain and output root-mean-square (RMS) noise, therefore obtains an improved sensitivity. Meanwhile, the Quasi-Miller RC network permits the charge amplifier to support ultra-low frequency operation without using a huge resistor, which is normally required by the charge amplifier. The fabricated charge amplifier demonstrates an input-referred RMS noise charge of 909 aC, a charge gain of 10.2 V/pC and a 3-dB bandwidth from 80 Hz to 38 MHz. Low noise and high charge gain are obtained simultaneously. Meanwhile, extremely low cut-off frequency is also obtained, which is beneficial to maintain the signal integrity.

Home-based health care applications are rapidly gaining popularity, enabling a renewed focus on the design of low-power and low-noise front-end circuitry. In this context, the evaluation of low-frequency biomedical signals, such as the respiration pattern, benefits from the design of a front-end amplifier with reduced power consumption and low noise. Continuous efforts on improving the performances of respiration-monitoring devices have resulted in the reduction of noise and motion artefacts by increasing complexity (e.g. complex algorithms or high precision filtering) at the expense of increased power consumption. This study is focused on the design of a fully integrated charge amplifier for respiration monitoring based on a pyroelectric sensor. Simulation and test results show a power consumption of 1.8 µW, an active die area of 0.085 mm 2 , a bandwidth in the range from 10 mHz to 13 kHz, and a remarkable noise efficiency factor of ∼2.79, which fits well with the development of an energy efficient wearable device.

The results and methodology of the experiment on the definition of impulse pressure, created by a generator of a plasma-impulse impact in oil, are described. Excessive impulse pressure was measured at a given distance from the axis of the generator in various samples of oil differing in their physical-chemical characteristics.

This paper presents a sub-baud-rate clock and data recovery (CDR) circuit that can recover clock and data using only differential quarter-rate clocks. A combination of eight samplers and an integrator recover four data bits in each clock cycle. Four of the eight samplers are re-used for phase detection as well as for background calibration to improve the robustness of the CDR to process, voltage, and temperature variations. A continuous-time linear equalizer is used to compensate for inter-symbol interference up to 11 dB. The CDR prototype fabricated in a 65-nm CMOS recovers 15.2-Gb/s data using only differential 3.8-GHz clock and achieves bit error rate (BER) 10-MHz jitter tolerance (JTOL) corner, and 548 fsrms recovered clock jitter. The total power consumption is 29 mW, which translates to an energy efficiency of 1.9 pJ/bit.

This paper presents a differential-input, differen tial-output charge amplifier topology built with discrete, commercial components. The amplifier is designed to interface high-impedance ultrasonic sensors made of piezoelectric polymer, with a required bandpass of at least 100 kHz to 1 MHz, and needs to operate from a single 5-V supply. The performance and tradeoffs of the proposed topology are evaluated analytically and using a circuit simulator, showing a charge-to-voltage conversion gain in excess of 240 dB[V/C], while maintaining an input impedance lower than 100 $\Omega$ . Simulations and measurements of a prototype implementation are presented.

A lossy integrator with active bias point

This paper presents a motion-sensing device with the capability of harvesting energy from low-frequency motion activities that can be utilized for long-term human health monitoring. The energy harvester used in the proposed motion sensor is based on the mechanical modulation of liquid on an insulated electrode, which utilizes a technique referred to as reverse electrowetting-on-dielectric (REWOD). The generated AC signal from the REWOD is rectified to a DC voltage using a Schottky diode-based rectifier and boosted subsequently with the help of a linear charge-pump circuit and a low-dropout regulator (LDO). The constant DC voltage from the LDO (1.8 V) powers the motion-sensing read-out circuitry, which converts the generated charge into a proportional output voltage using a charge amplifier. After amplification of the motion data, a 5-bit SAR-ADC (successive-approximation register ADC) digitizes the signal to be transmitted to a remote receiver. Both the CMOS energy harvester circuit including the rectifier, the charge-pump circuit, the LDO, and the read-out circuit including the charge amplifier, and the ADC is designed in the standard 180 nm CMOS technology. The amplified amplitude goes up to 1.76 V at 10 Hz motion frequency, following linearity with respect to the frequency. The generated DC voltage from the REWOD after the rectifier and the charge-pump is found to be 2.4 V, having the voltage conversion ratio (VCR) as 32.65% at 10 Hz of motion frequency. The power conversion efficiency (PCE) of the rectifier is simulated as high as 68.57% at 10 Hz. The LDO provides the power supply voltage of 1.8 V to the read-out circuit. The energy harvester demonstrates a linear relationship between the frequency of motion and the generated output power, making it suitable as a self-powered wearable motion sensor.

Charge amplifiers, characterized by their charge-sensitivity or charge gain, are essential components of a transducer-interfacing system that amplify charge signals emerging from various sensors and convert them into voltage signals. Today, with increased scaling of MOSFETs, it becomes challenging to obtain the charge amplifiers with high charge sensitivity and low power. Furthermore, if the charge amplifier is to be operated at lower bandwidth, then obtaining low noise at higher charge sensitivity is also difficult. In this paper, the authors propose a novel design of a charge-sensitive preamplifier in 90 nm CMOS technology that can be operated at the frequency range of 10 Hz-10 kHz, suitable for biosignals at lower frequencies. The opamp in the preamplifier is designed to have a folded-cascode structure with composite cascoding at its input transistors for low power operation. A feedback resistance of 185.20 GΩ for the preamplifier is actively realized using long-channel cascode MOSFET stage in the opamp, thereby eliminating the need for a large value of passive resistance on-chip. The preamplifier has a high charge sensitivity of 8.875 mV/fC at a low power consumption of 214.32 nW with input-referred noise of 256.89 μV for the bandwidth 10 Hz-10 kHz. The preamplifier operation is verified by interfacing the model of the preamplifier with the small-signal equivalent of a SPICE model of a Silicon Nanowire Field-effect Transistor (SiNW-FET) based biosensor which was proposed for impedimetric sensing of biomolecules.

Monitoring human health in real-time using wearable and implantable electronics (WIE) has become one of the most promising and rapidly growing technologies in the healthcare industry. In general, these electronics are powered by batteries that require periodic replacement and maintenance over their lifetime. To prolong the operation of these electronics, they should have zero post-installation maintenance. On this front, various energy harvesting technologies to generate electrical energy from ambient energy sources have been researched. Many energy harvesters currently available are limited by their power output and energy densities. With the miniaturization of wearable and implantable electronics, the size of the harvesters must be miniaturized accordingly in order to increase the energy density of the harvesters. Additionally, many of the energy harvesters also suffer from limited operational parameters such as resonance frequency and variable input signals. In this work, low frequency motion energy harvesting based on reverse electrowetting-ondielectric (REWOD) is examined using perforated high surface area electrodes with 38 µm pore diameters. Total available surface area per planar area was 8.36 cm2 showing a significant surface area enhancement from planar to porous electrodes and proportional increase in AC voltage density from our previous work. In REWOD energy harvesting, high surface area electrodes significantly increase the capacitance and hence the power density. An AC peak-to-peak voltage generation from the electrode in the range from 1.57-3.32 V for the given frequency range of 1-5 Hz with 0.5 Hz step is demonstrated. In addition, the unconditioned power generated from the harvester is converted to a DC power using a commercial off-theshelf Schottky diode-based voltage multiplier and low dropout regulator (LDO) such that the sensors that use this technology could be fully self-powered. The produced charge is then converted to a proportional voltage by using a commercial charge amplifier to record the features of the motion activities. A transceiver radio is also used to transmit the digitized data from the amplifier and the built-in analog-to-digital converter (ADC) in the micro-controller. This paper proposes the energy harvester acting as a self-powered motion sensor for different physical activities for wearable and wireless healthcare devices.

This paper presents a reverse electrowetting-on-dielectric (REWOD) energy harvester integrated with rectifier, boost converter, and charge amplifier that is, without bias voltage, capable of powering wearable sensors for monitoring human health in real-time. REWOD has been demonstrated to effectively generate electrical current at a low frequency range (< 3 Hz), which is the frequency range for various human activities such as walking, running, etc. However, the current generated from the REWOD without external bias source is insufficient to power such motion sensors. In this work, to eventually implement a fully self-powered motion sensor, we demonstrate a novel bias-free REWOD AC generation and then rectify, boost, and amplify the signal using commercial components. The unconditioned REWOD output of 95–240 mV AC is generated using a 50 μL droplet of 0.5M NaCl electrolyte and 2.5 mm of electrode displacement from an oscillation frequency range of 1–3 Hz. A seven-stage rectifier using Schottky diodes having a forward voltage drop of 135–240 mV and a forward current of 1 mA converts the generated AC signal to DC voltage. ∼3 V DC is measured at the boost converter output, proving the system could function as a self-powered motion sensor. Additionally, a linear relationship of output DC voltage with respect to frequency and displacement demonstrates the potential of this REWOD energy harvester to function as a self-powered wearable motion sensor.

This paper presents an inverter-based operational transconductance amplifier (OTA) which obtains high loop gain by correlated level shifting (CLS) technique with ping-pong operation. Thanks to the shifting capacitor providing voltage step between the OTA output and the inverter output, the suppressed inverter output swing helps OTA to achieve higher DC gain yielding better accuracy in the application of charge amplifier or integrator. The proposed technique utilizes two identical sub-OTA structures working in the ping-pong way to provide level shifting reference voltage for each other. This operation allows inverter-based OTA to work at the amplification mode in both clock phases, thus double sampling technique can be adopted to achieve twice of the charge transfer efficiency. Compared with the conventional inverter-based charge amplifier, the proposed topology improves DC gain from 39dB to 71dB at the cost of 17% power consumption increase from 7.1µA to 8.6µA.

In this work, a piezoelectric MEMS based vibration sensor with a unique gimbal shaped guard ring in differential electrical configuration has been designed for enhanced acceleration sensitivity in out-of-plane direction and reduced in-plane crosstalk. The Thin-film Piezo on Silicon (TPoS) accelerometer was fabricated using a GlobalMEMS Inc. PZT platform. This method makes use of the excellent piezoelectric property of the Lead Zirconate Titanate (PZT) thin-film along with low crystal defect property of single crystal silicon, thus ensuring a good combination of sensitivity, resolution, bandwidth, reliability, and lifetime. A system-level approach was adopted to integrate the MEMS device with a charge amplifier and a microcontroller. The device performance was compared with the standard reference accelerometer for 1-g load. The developed MEMS sensor module was further implemented for surface roughness prediction in a quartz polishing system using machine learning algorithm incorporating both the acceleration-time data and the feed rate of the polishing spindle.

We describe a common-mode feedback circuit (CMFB) for a charge detector. The amplifier is implemented in a 180-nm complementary metal-oxide-semiconductor (CMOS) process. The amplifier combines a folded differential topology, active reset, and small feedback capacitors. This allows for low noise, high-gain, high-dynamic-range, and robust operations. The design and analysis of the CMFB for the proposed high-gain charge amplifier is discussed. Simulation results show that the CMFB loop has a phase margin of 62.1 degrees and a gain margin of 25 dB. Measurement results show the amplifier chip exhibits a stable common mode voltage.

This paper presents a self-powered motion sensor based on reverse-electrowetting on dielectric (REWOD) energy harvesting having the capability of remotely keeping a track of any motion activity. The energy harvester includes a rectifier and a voltage regulator to provide the DC supply voltage to the analog front-end and the transmitter to wirelessly transfer the data from the motion sensor. The on-chip circuitry includes a seven-stage voltage-doubler based rectifier, an amplifier, an analog-to-digital converter (ADC), and a transmitter, and is designed in standard 180 nm CMOS process with a supply voltage of 1.8 V. The recycled folded cascode (RFC) based charge amplifier has a closed-loop gain of 53 dB within the bandwidth of 1–150 Hz, which is suitable to detect any low-frequency motion signal. An 8-bit SAR-ADC is designed to digitize the amplified signal with a sampling rate of 1 ksamples/s. The transmitter used for this application operates in the 3.1–5 GHz frequency band with an energy efficiency of 8.5 pJ/pulse at 100 kbps data rate. The wireless motion sensing device with the REWOD can be suitable for quantitatively monitoring the motion-related data as a wearable sensor.

A detector connected to a charge amplifier adds parasitic input capacitance that alters the amplifier's gain. The detector capacitance therefore must be characterized so as to properly account for its effect. This paper presents a novel, compact technique to measure the detector capacitance by exploiting the circuit elements within the charge amplifier itself. Reconfiguring the charge amplifier with programmable switches, a capacitor divider network emerges to measure the detector capacitance without the need for any accurate timing references and complex controls. Experimental results of the proposed charge amplifier fabricated in a 180-nm CMOS technology demonstrate the ability to measure the detector capacitance to within 3% of its actual value. An actual charge measurement is also presented.

The paper theoretically determines the dependence of the electrically excited noise, damped oscillations piezoelectric sensor, integrated with SWCNT (single-wall carbon nanotube) needle and charge amplifier, from defects of an SWCNT graphene sheet and sensor malfunctions generally, for AFM (atomic force microscopy) with high-resolution. Also is the proposed method for estimating the piezoelectric sensor state, integrated with the SWCNT needle and charge amplifier when evaluating “SWCNT needle-surface” contact in real-time scanning AFM. Many micro-machining techniques have been employed to fabricate signal oscillations piezoelectric sensors and piezoelectric nanoactuators. The properties of SWCNT, for example, high strength, many times greater than the strength of steel, makes them suitable elements for use as needles probe microscopy. This paper presents both experimental and analytical data to show the critical characteristics of a piezoelectric sensor, integrated with SWCNT needle contact in the real-time scanning AFM.

Bistable laminated composites are attractive for morphing structures because they can hold deformed stable shapes without any external energy and require actuation only to switch between shapes. They offer opportunities for shape morphing, energy harvesting, and flow control devices. Piezoelectric macrofiber composites (MFC) embedded in bistable laminates have been demonstrated for actuation and energy harvesting. However, their relatively high stiffness, relatively complex architecture, and arbitrary fiber orientation limit their ability to sense shape change in bistable laminates. There has been little work on the integration of sensing methods to monitor an adaptive structure’s shape; shape sensing has been investigated mainly for the detection of snap-through events. In this paper, we present self-sensing curved bistable laminates layered with piezoelectric PVDF films that can sense smooth changes as well as abrupt snap-through transitions. Measurement of smooth changes in the laminate’s curvature is enabled by an automated drift compensation charge amplifier with an extremely low cutoff frequency of 0.01 mHz. The sensing function is demonstrated on bistable laminates created using mechanical prestress. Two sensor layers are configured in the composite such that one measures change in curvature and the other measures snap-through response. The shapes measured by the sensor in terms of voltage correlate well with the shapes measured with a 3D motion capture system. An analytical model is developed to relate curvature change to voltage output and is found to be in good agreement with the measured curvature-voltage sensitivities. The weakly coupled shapes of the laminate and the low cross sensitivity of PVDF enable real-time measurement of the principal curvatures.

PolyVinyliDene Fluoride (PVDF) energy harvesters have been observed to possess the ability to detect leak and damage in pipes they are bonded to by monitoring their vibration energy harvested due to fluid flow, measured as open circuit voltage. Consequently, they can be employed as structural health monitoring (SHM) sensors for such applications. To make this energy harvesting based SHM an effective measurement methodology, the harvested energy should be demonstrably passed through a piezoelectric measuring chain and the results obtained should be calibrated appropriately. This paper addresses this problem by designing a custom-made three-channel dual-stage charge amplifier as signal conditioner and validating the measuring chain. The charge amplifier ensures that the voltage generated by the PVDF harvester is measured accurately and remains proportional to the strain responses for the monitored structure and constitutes a part of the piezoelectric measuring chain. A two-stage validation process was employed in this work. The first stage is a general validation exercise serving as a check for measuring chain intrinsic noise and general performance while the second stage is an application-specific validation exercise that serves to estimate the performance of the measuring chain for the target application. The suitability of using the measuring chain for the application of vibration energy harvesting based SHM is demonstrated through the result of this validation process.

With the advanced technologies such as 5 G network and internet of things (IoT), there are incredibly increasing sensors and corresponding applications emerging to benefit our daily lives. However, the power supplies for countless sensors become a serious issue to suppress further expansion of IoT. In this work, a self-powered triboelectric sensor (CN-STS) made of electrospun composite nanofibers is developed towards smart traffic monitoring and management. To meet the requirements of fast-response and high sensitivity for the smart traffic management, transferred charge density is adopted as sensing signals compared to voltage / current outputs for it can perfectly record the subtle differences and suitable for dynamic traffic monitoring. Carbon nanotube is further doped into PVDF nanofibers to improve the electrical output performance and pressure sensitivity. A relatively high sensitivity of 0.0406 μ Cm-2kPa-1 at low pressure range (0 to 75 kPa) and a sensitivity of 0.0032 μ Cm-2kPa-1 at higher pressure range (75 to 425 kPa) can be achieved by the CN-STS, indicating that the CN-STS is more sensitive at low pressure range. Moreover, by connecting to cloud IoT services, the functions of traffic flow management, overlapping and speeding vehicle capturing, and plate number recognition are realized by the CN-STS arrays with a compensation circuit. A charge amplifier is utilized in power management to process the charge input signals for better distinguishing the signals from none-vehicles and stabilize the volage output for further reading by the A/D convertor build in Raspberry Pi. The engineered self-powered triboelectric sensors not only open a new potential area for triboelectric nanogenerators but also significantly popularize the IoT industry.

A digital closed-loop system design of a microelectromechanical systems (MEMS) disk resonator gyroscope (DRG) is proposed in this paper. Vibration models with non-ideal factors are provided based on the structure characteristics and operation mode of the sensing element. The DRG operates in force balance mode with four control loops. A closed self-excited loop realizes stable vibration amplitude on the basis of peak detection technology and phase control loop. Force-to-rebalance technology is employed for the closed sense loop. A high-frequency carrier loaded on an anchor weakens the effect of parasitic capacitances coupling. The signal detected by the charge amplifier is demodulated and converted into a digital output for subsequent processing. Considering compatibility with digital circuits and output precision demands, a low passband sigma-delta (&Sigma, &Delta, ) analog-to-digital converter (ADC) is implemented with a 111.8dB signal-to-noise ratio (SNR). The analog front-end and digital closed self-excited loop is manufactured with a standard 0.35 &micro, m complementary metal-oxide-semiconductor (CMOS) technology. The experimental results show a bias instability of 2.1 &deg, /h and a nonlinearity of 0.035% over the &plusmn, 400&deg, full-scale range.

We report the characterisation and calibration of a new laser pulse energy measurement device, developed for pico-joule pulse energy measurement at repetition rates up to 1 kHz. The device comprises a charge integration amplifier operating in conjunction with an input charge source; a light trapping photo-detector, which converts an incident laser pulse to a charge pulse. The novel amplifier individually integrates each charge pulse from the source and outputs a corresponding 20-bit resolution digital signal. This signal is converted to pulse energy through post processing, knowing the absolute responsivity of the photodiode detector and the calibration factors of the charge amplifier. A differential evolution algorithm is used to determine optimised values for the feedback capacitors of the amplifier, the amplifier gain and offset. The values measured by the new laser pulse energy meter were compared with those obtained from measurements traceable to both the high and low-level laser pulse energy scales maintained by NIST, Boulder. These were consistent within the combined expanded measurement uncertainty. This new device offers lower uncertainty and portability, suitable for field use.

This study is dedicated to design an in-cell active-matrix capacitive (IAMC) touch panel and its readout circuitry. This IAMC touch panel is in a structure that embeds all components for touch panel in a standard active matrix display. In this way, the thickness of the display-touch combined module can be significantly reduced, but introducing much noise from display to touch module, leading to higher mis-judgements on touches. To solve the problem, this study proposes a new readout circuit and digital signal processing techniques to tackle well the aforementioned noise for much accurate touch sensing. The readout consists essentially of an analog front-end switched capacitor charge amplifier (SCCA), a 12-bit SAR ADC and a digital signal processing (DSP) unit for calibration and filtering. A field-programmable gate array (FPGA) board is adopted to implement the designed digital signal processing in practice. The performance of the readout is tested for a 5 × 12, 0.88-inch IAMC touch panel with a scanning frequency of 200 Hz. Experimental data show clearly that the sensed capacitance was successfully converted to 200 digits in a full dynamic range of 12-bits and a SNR of 52 dB, which facilitates well accurate determination of touches and locations on an IAMC touch panel.

A model of a High Voltage CMOS (HV-CMOS) Monolithic Active Pixel Sensor (MAPS) has been modelled using Technology Computer Aided Design (TCAD). The model has incorporated both the active region and the on-pixel readout circuits which were comprised of a source follower amplifier and an integrated charge amplifier. The simulation has examined the electrical characteristics and response output of a HV-CMOS MAPS sensor using typical dimensions, levels of doping in the structural layers and bias conditions for this sensor. The performance of two alternate designs of amplifier have been examined as a function of the operating parameters. The response of the sensor to the incidence of Minimum Ionizing Particles (MIPs) at different energies has been included in the model.

Розглянуто питання щодо вибору оптимальної схемотехнічної моделі біморфного п'єзо-елемента динамічних тисків з двоконтуровим від'ємним зворотним зв'язком та досліджено характеристики п'єзоперетворювачів з вихідним підсилювачем заряду та підсилювачем напру- ги в додатковому каналі зворотного зв'язку. Issues related to the selection of the optimized circuit model of a bimorph piezoelectric element of dynamic pressure with dual-circuit inverse feedback are reviewed. Characteristics of piezoelectric transducers with source charge amplifier and voltage amplifier in additional feedback path are investigated.

This paper is concerned with the experimental characterization of a charge sensitive amplifier featuring dynamic signal compression, fast recovery time, low noise, and reduced area occupancy. The device takes the advantage of the nonlinear characteristic of a feedback transistor that behaves like a voltage-controlled capacitance. This property has been exploited to fit a wide input dynamic range into the available output swing. The charge amplifier can be operated in synchronous mode at high frame rates, of the order of few megahertz, thanks to a wide bandwidth, an improved output stage, and a fast reset network. Thanks to the small area occupancy, the amplifier is suitable for integration in a $100\times 100\,\,\mu \text {m}^{2}$ pixel area. All these features make the device a good candidate for applications where a fast front end with a nonlinear response is required, such as in imaging instrumentation for free electron laser experiments. The aim of this paper is to present and discuss the experimental results coming from the characterization of the first prototype of the circuit, which has been designed in a 65-nm CMOS technology. This paper has been carried out in the frame of the PixFEL Project funded by the Istituto Nazionale di Fisica Nucleare, Italy.

In this paper, we have proposed an input interfacing scheme with differential output for integrated capacitive sensor applications. In the proposed scheme, the front-end interfacing is based on switched capacitor charge amplifier configuration using a fully differential operational transconductance amplifier and one differential capacitive sensor arrangement which provides differential output with minimum number of circuit components. In the back end, a sigma–delta ( $\Sigma \Delta $ ) modulator is integrated for modulated digital output. The signal conditioning circuit also includes gain programmability by selecting proper feedback capacitor and mismatch cancellation between the sensing capacitors through on-chip capacitors array. The complete application specific integrated circuit (ASIC) is designed and fabricated in United Microelectronics Corporation (UMC) $0.18-\mu \text{m}$ CMOS process technology. The fabricated ASIC is then integrated with a silicon-on-insulator microelectromechnical systems capacitive accelerometer to test and characterize the performance of the proposed scheme. The measured result shows that the sensitivity of the proposed circuit can be varied from 200 to 900 mV/g by changing the feedback capacitor. The integrated system is also tested with electrostatic actuation as well as with a vibrating shaker and the measurement results are presented.

An improved topology for the baseband super-regenerative sampling amplifier is proposed and analyzed, which employs a series-capacitors output load to realize positive feedback. As in the conventional circuit, the gain of the amplifier is continuously variable by controlling the length of the capacitor charging phase. It is shown that decreasing feedback enhances the linearity of the circuit while trading off with a lower sampling speed. Entirely removing the feedback yields the integrating amplifier circuit. This is a practical implementation in terms of linearity, power, noise, and gain in low-frequency applications, including biomedical signal amplification. The analysis is verified by measured results from an integrated circuit prototype in 180-nm CMOS technology.

Silicon photomultipliers (SiPMs) offer advantages such as lower relative cost, smaller size, and lower operating voltages compared to photomultiplier tubes. A SiPM’s readout circuit topology can significantly affect the characteristics of an imaging array. In nuclear imaging and detection, energy, timing, and position are the primary characteristics of interest. Nuclear imaging has applications in the medical, astronomy, and high energy physics fields, making SiPMs an active research area. This work is focused on the circuit topologies required for nuclear imaging. We surveyed the readout strategies including the front end preamplification topology choices of transimpedance amplifier, charge amplifier, and voltage amplifier. In addition, a review of circuit topologies suitable for energy, timing, and position information extraction was performed along with a summary of performance limitations and current challenges.

A comprehensive noise model of a junction gate field-effect transistor (JFET) charge amplifier is presented for applications with piezoelectric sensors. Based on this previously reported amplifier structure, a noise equivalent circuit is derived and discussed. Universal noise gain expressions for each of the twelve considered noise sources are given. By means of an analytical description of the charge amplifier’s noise behavior, the design and optimization of such preamplifiers for various capacitive microelectromechanical sensor systems will be distinctly simplified. Calculations of the noise floor are compared with measurements with a cantilever-type magnetoelectric sensor and with the performance of a so far commonly utilized basic charge amplifier. With the JFET charge amplifier a noise reduction of approximately 22 dB is achieved in the vicinity of the utilized sensor’s resonance frequency of 7.45 kHz. The reported amplifier is the first which has no negative influence on the total noise level of a resonant magnetoelectric sensor system.

In this study, we successfully developed a high signal-to-noise ratio (SNR) rangefinder based on a piezoelectric micromachined ultrasonic transducer (pMUT). A c-axis-oriented Pb(Mn1/3,Nb2/3)O3-Pb(Zr,Ti)O3 (PMnN-PZT) epitaxial thin film was employed as a piezoelectric transducer considering its outstanding figures-of-merit for SNR, due to the high piezoelectric coefficient and small relative permittivity (typical values: e31,f = −14C/m2, er = 200–300). The pMUTs was based on an epitaxial PMnN-PZT/Si diaphragm structure and prototyped from a SOI substrate; its rangefinding ability was evaluated with a pair of devices, specifically, transmitter and receiver, respectively. As a result, the maximum range was estimated to be over 2 m at a low actuating voltage of 1 Vp-p, when 12 dB was set as the threshold SNR. The energy consumption of the transmitter was as small as ∼5 nJ for the generation of a 50-cycle ultrasonic burst. The noise analysis of the receiver’s charge amplifier circuit indicated that this system could be improved by the optimization of bandwidth and by eliminating external noise. We believe that this high performance pMUT rangefinder will be utilized in various applications of consumer electronics or as an alternative to the bulk piezoelectric ceramic rangefinder in the near future.

Integrators are an important functional module of several filters, PID controllers and automated systems. Designing these integrators in fractional domain enhance their operations and make the responses highly precise and accurate. This paper presents a Fractional Order Current Integrator using second generation current conveyor as the active block, and fractional capacitor as a grounded fractance. Analog realization of this fractance comprises of resistances and capacitances arranged in parallel RC ladder topology. The motivation behind this work is that more accurate and stable fractional integrator with fewer passive elements, for lower bias voltage and high dynamic range, can be designed and implemented. Integrators of fractional orders from 0.1 to 0.9 are simulated using TSMC 0.25 µm technology parameters. The transient and frequency responses obtained in Mentor Graphics are in close conformity with the theoretical values of magnitude and phase. Robustness of the proposed model is verified by performing Monte Carlo analysis in time and in frequency domain. Comparisons of fractional order current integrators with existing analog fractance models have also been included to further validate the work presented in the paper.

In this paper, a new tomography technique called electrical charge tomography for two-phase flow imaging is presented. The probe consists of few pair of electrodes which are electrically energized to generate electrical charges within the fluid under test. The intensity of these charges depends on the chemical and physical properties of the fluid, as well as to its molecular distribution. Another group of electrodes surrounding the cross section of the fluid under test are used to capture the induced electrical charges. These are then converted into an electrical signal using a high sensitive charge amplifier. A postprocessing unit which consists of an analog to digital converter, followed by an field programmable gate array (FPGA) module is then used for high level signal processing (i.e., a dedicated dynamic thresholding algorithm) and image reconstruction. Experimental results demonstrate the capability of the system to accurately generate 2-D cross-sectional images, where the error is lower by up to 14% when using another electrical capacitance (ECT) tomography probe. The other advantage of this technique over ECT is the reduced data acquisition time, since in ECT a minimum time is required for the charge and discharge of the capacitance in order to achieve acceptable accuracy. This makes the probe another attractive concept for future tomography systems targeting real-time applications.

The development of a DC magnetic field sensor based on a magnetoelectric (ME) PVDF/Metglas composite is reported. The ME sensing composite has a resonance frequency close to 25.4 kHz, a linear response (r2=0.997) in the 0-2Oe DC magnetic field range and a maximum output voltage of 112 mV (related to a ME voltage coefficient α33 of ≈30 V.cm-1.Oe-1). By incorporating a charge amplifier, an AC-RMS converter and a microcontroller on chip peripheric analog to digital converter (ADC) the ME voltage response is not distorted, the linearity is maintained and the ME output voltage increases to 3.3V (α33effective=1000 V.cm-1.Oe-1). The sensing device, including the readout electronics, has maximum drift of 0.12 Oe with an average total drift of 0.04 Oe, with a sensitivity of 1.5 V.Oe-1 (15 kV.T-1) and a 70nT resolution. This features compares favourably with a reference Hall sensor that showed a maximum drift of 0.07 Oe and an average error of 0.16 Oe, 5 V.T-1 sensitivity and 2 μT resolution. Those features allied to the accurate measurement of the HDC fields in the 0-2 Oe range make this polymer-based device very attractive for applications such as Earth magnetic field sensing, digital compasses, navigation and magnetic field anomaly detectors, among others., Foundation for Science and Technology (FCT) in the framework of the Strategic Funding UID/FIS/04650/2013 under Project PTDC/EEI-SII/5582/2014, and in part by the Basque Government In- dustry Department under the ELKARTEK Program. The work of P. Mar- tins, V. Correia, S. Reis, and M. P. Silva was supported by the FCT under Grant SFRH/BPD/96227/2013, Grant SFRH/BPD/97739/2013, Grant SFRH/BDE/406, and Grant SFRH/BD/70303/2010. The work of S. Lanceros-Mendez was supported in part by the Provincial Council of Bizkaia under the Bizkaia Talent Program, in part by the European Union’s Seventh Framework Program, and in part by the Marie Curie Actions, info:eu-repo/semantics/publishedVersion