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Since the introduction of adaptive systems for corrective measures, static and dynamic disturbances have been reduced through the manipulation of surface shape in a well-controlled manner. One important application where adaptive systems are highly needed is in the future photo-lithography machines, particularly the wafer table where disturbances affect overlay and focus performance. To reduce overlay and focus errors, a dense array of actuators must be integrated into the wafer table to apply both in- and out-of-plane corrective deformations to the wafer surface. To realize a certain wafer shape, influence functions are linearly superimposed. Accurate models of the influence functions result in an accurate prediction of the final wafer shape. To reduce calibration errors, the influence function of every actuator needs to be determined. Here, we propose a technique to rapidly measure the influence function: the influence function measurement (IFM) technique. Using the actuate-sense property of piezoelectric materials, the influence function is determined by activating one piezo-actuator and measuring the charge induced on the neighboring piezo-actuators. The measured charges are compared to the results of finite element simulations and the absolute difference of 0.3 % is reported for the inter-actuator charge coupling parameters. This clearly indicates the potential of the proposed technique. Note to Practitioners—A critical step during the integrated-circuit lithographic fabrication process is the exposure. A particular practical challenge in this step is to correct for the mismatch between the optical image plane and the wafer surface, caused by wafer deformations. The mismatch negatively impacts the overlay and focus performance. To reduce the mismatch, actuators can be embedded into the wafer table to counteract wafer deformations, where the overall wafer surface shape is a superposition of each actuator’s influence function. As part of the calibration for the embedded actuators, their influence functions are measured and stored. However, errors arise when influence functions are not measured for every actuator. Additionally, for different wafers, the influence functions vary hence the calibration should be done per wafer. This calibration process takes time and should not influence throughput. Our paper presents a viable approach that reduces the calibration time of active wafer tables, which is also relevant for other adaptive systems such as deformable mirrors. Since the technique requires the actuators to be mechanically coupled, it is limited to continuous surfaces. The proposed technique is numerically tested and experimentally verified to demonstrate performance. [ABSTRACT FROM AUTHOR]

Electrocardiogram (ECG) records the electrical activity of the heart and is the most significant diagnostic indicator of health. The electrical activity propagates towards the skin and is typically measured using gel silver/silver chloride (Ag/AgCl) electrodes. The quality of the measured signal depends on the amplitude of the electrical activity, the conductivity of the tissues and skin, and that of the measuring electrode. Gel electrodes can cause skin irritability and are not suitable for long-term measurements requiring the diagnosis of paroxysmal arrhythmias. Dry electrodes are comparatively comfortable to wear but are highly dependent on body hair, sweating, and movement. Non-contact electrodes on the other hand avoid ohmic contact with the skin by providing a capacitive coupling between the skin and the electrode. They can be easily worn over clothing or can be measured from a distance. However, motion artefact remains the biggest challenge in such systems. This study proposes a novel two-channel circuitry for ECG acquisition along with a mathematical model to mitigate the effect of changing sensor-electrode capacitance in non-contact sensors. This method was modeled and validated at different sensor-electrode positions or air-gaps. The effect of change in mutual and parasitic capacitance between the sensor's channels, body tissue impedance, and the ratio of the areas of the two channels was also analysed in terms of Signal to Noise Ratio (SNR). The highest SNRs were achieved with smaller air-gaps and higher ratios of channels' areas. [Display omitted] • Motion artefact remains a major challenge in ambulatory and capacitive Electrocardiogram monitoring. • A novel technology that can be used for long-term and efficiently reject/eliminate motion artefacts has been proposed. • Signal reconstruction was possible using a two-channel electronic circuit and mathematical equations. • This study considered mutual and parasitic capacitances, tissue impedances, and electrode area changes. [ABSTRACT FROM AUTHOR]

We describe a charge detector that utilizes a high-gain, differential solid-state amplifier with active reset and a novel technique to measure the gain using a custom optoelectronic system. Implemented in a 180-nm complementary metal–oxide–semiconductor (CMOS) process, the amplifier realizes a high gain of $8.9~\mu \text{V}/\text{e}-$ and single-pass rms noise of 475e− for 10-ms time interval with a 300-kHz low-pass filter corner. Operating at a sampling frequency of 10 kHz, the active reset extends the dynamic range of the detector. The amplifier is the first instance of a charge detector that combines a differential topology, active reset, and small feedback capacitors for low-noise, high-gain, high-dynamic-range, and robust operations. The proposed optoelectronic test system injects an adjustable input photocurrent as low as 33 pA to precisely quantify the detector’s gain without the need for a known calibration capacitance. The amplifier is directly wire-bonded to a PCB that has a built-in 1-cm2 Faraday cup. The gain and noise performance have been characterized for a range of input capacitance, and the results show good agreement with simulations. The test system additionally demonstrates the ability to inject a time-varying input at the picoamphere levels to characterize the dynamic response of the detector. An electrospray system confirms that the detector responds to free-space charge and that it can process an input as large as 56 000e− without saturation. The compact and high sensitivity design qualify the device for use in charge detection applications, such as mass spectrometry and space instruments. [ABSTRACT FROM AUTHOR]

A low-power ultrasonic communication front end conceived for cargo container monitoring is presented. Two piezoelectric transducers (PTs) operating at 40 kHz are fixed to the metallic wall by means of a customized magnetic case, allowing a noninvasive inside–outside communication preserving the container integrity. Once the resulting ultrasonic channel is characterized, an experimental measurement setup based on field-programmable gate array (FPGA) is implemented for testing 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 differential binary phase-shift keying (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 kb/s) architectures based on the previous elements are presented. All the proposed contributions are experimentally validated. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

We present a measurement system capable to detect and reconstruct the trajectory of moving charged debris expelled with the exhaust gases or circulating in the lubricating oil of engines, aero-engines, or gas turbines. The measurement technique is based on a circular array of three electrostatic sensors used to estimate the trajectory, the charge, and the velocity of a moving charged particle. We discuss methods to process the information provided by the sensors, combining physical models and the geometrical characteristics of the sensor array, providing a theoretical characterization of the measurement accuracy, which is shown to be not dependent on the direction of the particle motion with respect to the sensor placement. The information obtained with the measurement system can be used to reject false positives when the sensors and the front-end electronics are used in noisy environments. [ABSTRACT FROM AUTHOR]

The measurement of the operating deflection shape (ODS) of power transmission belts is of great importance for the fault diagnosis and prognosis of industrial belt drive systems. This paper presents a novel method based on an electrostatic sensor array to measure the ODS of a belt moving both axially and transversely. The electrostatic sensor integrates a charge amplifier that converts the induced charge on a strip-shaped electrode into a voltage signal. Finite-element simulations are performed to study the sensing characteristics of the sensor and the results reveal that the sensor can respond to vibration displacement. Construction of the ODS is achieved in the frequency domain using the ODS frequency response function. Comparative experimental studies with a high-accuracy laser displacement sensor were conducted on a purpose-built test rig and the results show that the vibration frequencies and their relative magnitudes obtained from both sensors agree well with each other. Experiments conducted over a range of belt axial speeds show that the belt vibrates at frequencies that are well separated and identifiable using a peak picking method. The measured ODSs of the first three vibration modes illustrate that the vibration displacement is larger in the middle of the belt span than at both ends and that the phase shift relative to the reference sensor at each measurement point increases monotonically along the belt running direction. The belt axial speed determines the vibration frequencies and displacement, which reaches the maximum amplitude around the natural frequency of the belt. [ABSTRACT FROM AUTHOR]

Using a bulk Micro-Megas (MM) detector an energy measurement can be obtained collecting the total charge reaching the mesh electrode connected to a low noise charge sensitive preamplifier. When operating such a device in a low-pressure gas regime, it is necessary to modify the amplification gap geometry to reach the optimal detector gain. This implies changes in the input capacitance of the preamplifier influencing its signal to noise ratio and thus the detector energy resolution. An ad-hoc high-gain and low-noise charge preamplifier has been developed to cope with the requirements of our application field. In this short report, we present the development activities focused to the study of a configurable charge amplifier to be connected to a MM detector having different mesh capacitances. [ABSTRACT FROM AUTHOR]

We present the design and noise performance of a fully cryogenic ( $$T=4$$ K) high-electron mobility transistor (HEMT)-based charge amplifier for readout of sub-kelvin semiconductor radiation detectors. The amplifier is being developed for use in direct detection dark matter searches such as the cryogenic dark matter search and will allow these experiments to probe weakly interacting massive particle masses below 10 GeV/ $$c^2$$ while retaining background discrimination. The amplifier dissipates $$\approx $$ 1 mW of power and provides an open loop voltage gain of several hundreds. The measured noise performance is better than that of JFET-based charge amplifiers and is dominated by the noise of the input HEMT. An optimal filter calculation using the measured closed loop noise and typical detector characteristics predicts a charge resolution of $$\sigma _q$$ =106 eV (35 electrons) for leakage currents below $$4 \times 10^{-15}$$ A. [ABSTRACT FROM AUTHOR]

Voltage drift over time in charge amplifiers is a problem not fully solved yet for DC measurements and continues to be a challenge for the scientific community. In this study we analyse the factors that cause this unwanted effect and propose a new method to compensate it. An automatic electronic circuit compensates the drift effect in two stages: first, a closed-loop proportional–integral control is used to bring the output voltage of the charge amplifier to zero and hold it while no measurement is being taken; and second, the voltage drift is compensated with an open-loop control when measurement is being taken. The proposed method allows us to compensate the voltage drift whatever its magnitude. Simulation and experimental results show that the drift effect in the output voltage of the charge amplifier is attenuated up to 99%. • Performance of a controlled charge amplifier for DC applications. • Compensation of large parasitic DC leakage currents for removing voltage drift. • Voltage drift compensation before and while measurements are taken. [ABSTRACT FROM AUTHOR]

Background: During the process of cell micro operation, the contact force between the entry needle and the cell membrane is usually a very small area to be tested.Objective: These two features have been utilized to design a high precision micro force sensor to provide a force feedback in the process of cell micro operation.Methods: However, PVDF (Polyvinylidene Fluoride) has continued to display both a wide range of frequency response and a highly sensitive transform between force and electricity. In this paper a charge signal is obtained. In order to transform the charge signal into a voltage signal, a signal processing circuit was designed. The data acquisition card PCI-6221 (National Instruments) was used. It was employed to collect the voltage signal.Results: The resultant micro force sensor was calibrated by using a rating test.Conclusions: The experimental test results demonstrated that the sensitivity and linearity of the designed micro force sensor were higher than the sensitivity and linearity of a traditional piezoelectric sensor. [ABSTRACT FROM AUTHOR]

The electrostatic detection of gas path debris has been proposed in literature as a tool to monitor mechanical component faults along the combustion gas path of turbo-machines. In this paper we discuss the general theoretical characterization of a debris detection monitoring system based on electrostatic sensors and charge amplifiers. We first provide the analytical expression of the time-varying charge induced by the moving debris on the sensor surface. After introducing a simplified electric model of the charge amplifier, we discuss the effects of the amplifier bandwidth on the shape of the output voltage signal. Theoretical results have been validated with experiments. [ABSTRACT FROM AUTHOR]

It is shown theoretically and by experimentation that the ac stray immune capacitance meter based on the charge amplifier circuit can be modified to reduce the effects of the parasitic capacitance across the feedback capacitor. This is achieved by simply introducing a unity gain buffer amplifier within the circuit loop. [ABSTRACT FROM PUBLISHER]

This paper proposes and describes a charge amplifier-based interface electronics design methodology approach for piezoelectric polymer tactile sensors to be used for humanoid robot applications. The tactile sensor-consisting of a PVDF single sensor element-is illustrated, the electromechanical thickness mode behavior is modeled and a fabricated prototype is presented. The model allows associating the PVDF charge response to the effective load applied on the outer surface of the sensor. The model is also used as a key in the proposed design methodology to estimate the charge to be detected by the charge amplifier. A case study based on the design methodology approach is reported. The system (PVDF single taxel + interface electronics) is analyzed firstly, considering it as ideal and then when the nonidealities come into play. A charge amplifier-based interface electronics prototype is also presented. The implementation is used to validate the followed approach and then defining the design specs towards the dedicated IC design. Some experimental results are also reported. [ABSTRACT FROM AUTHOR]

This manuscript introduces a transistor level technique that results in simultaneous improved slew rate and noise performance for applications where only the final settled output voltage over a predefined time frame is important — such as silicon detector read out charge-to-voltage reset amplifiers. For large signal swings, slew limitation is detected and compensated dynamically. For non-slew limiting situations the amplifier operates normally in a low noise mode. To verify correct operation of the dynamic slew correction circuit, a single-ended, pulse-reset charge amplifier was fabricated in IBM 130 nm 6M/2P technology. The test amplifier achieved a slew rate of 1V/120 ns with a 50 pF load and a total of \sim 23 \mu\!Vrms noise over 100 kHz–20 MHz . The reported amplifier also serves as the basis for the high performance front-end amplifier in the LPD detector system for the European XFEL. [ABSTRACT FROM PUBLISHER]

The adoption of charge‐mode amplification, rather than the classical voltage‐mode, to interface piezoelectric interdigital transducers made of polymer film to the data acquisition electronics is described. The circuit and operating principles of a charge amplifier are briefly explained, followed by the experimental comparison of a charge amplifier implementation with a solution based on an instrumentation amplifier. The experiments, based on A0‐mode Lamb wave transmission over an aluminium plate, demonstrate the effectiveness of charge‐mode interfacing and its insensitivity to cable loading. [ABSTRACT FROM AUTHOR]

The optimization of the noise performance of integrated complementary metal-oxide semiconductor (CMOS) charge amplifiers is studied in detail considering accurate 1/f noise modeling for the input metal-oxide semiconductor field-effect transistor (MOSFET) biased in a strong inversion-saturation region. This paper aims to generalize and correct previously published analyses which have been based on two limiting and sometimes not applicable assumptions: a fixed MOSFETs bias current and the general validity of the McWhorter 1/f noise model. This study considers the two main 1/f noise models: 1) the mobility fluctuation, known as Δμ or Hooge model, which is followed by p-channel MOSFETs and 2) the carriers number fluctuation, also known as or ΔN McWhorter model, which is applicable only for n-channel MOSFETs. The front-end noise optimization is made with the 1/f component alone, thus determining the ultimate performance, and also considering the presence of series and parallel white noise sources. It is shown that different design criteria are valid of p-or n-channel MOSFETs: the Δμ model results in an optimum bias current and a different optimum gate width with respect to ΔN model. Two-dimensions suboptimum noise minimization criteria are derived when power or area constraints are imposed to the circuit design. Starting from experimental data on CMOS 1/f noise, examples of application of the presented analysis are shown to predict the lower limits of the i/f noise contribution for the currently available CMOS technologies. [ABSTRACT FROM AUTHOR]

This paper presents a capacitive-sensor interface with high accuracy and excellent stability. The range of the measured capacitance is up to 1 pF. The implemented circuit tolerates cable capacitances of up to 1 nF. Depending on the operation mode, the conversion time varies between 39 and 100 μs. The measurement principle permits a mode with compensation of small sensor leakage currents. The reference units are frequency, resistance, and resistance ratios, which provide high initial accuracy and a long-term stability. The measured temperature coefficient of the capacitance converter is about 2 ppm/K. A special multislope analog-to-digital conversion (ADC) is used, which, to increase the resolution, transfers itself at the beginning and at the end of the conversion process into an oversampling conversion. Based on the band-pass filtering function of the implemented ADC technique and the low-noise input stage used, a dynamic range of better than 14 b has been achieved for a cable capacitance that is less than 400 pF. [ABSTRACT FROM AUTHOR]

In this paper, an all-analog pixel architecture for the readout of X-ray pixel detectors with multiple energy discrimination is proposed. The circuit comprises a self-triggered reset charge amplifier and three distinct channels devoted to the detection on a specific energy band. Each channel is composed of an autocalibrated comparator, an energy window identification logic, and an analog counter with an adjustable dynamic range. A test prototype has been implemented with a standard complementary metal-oxide-semiconductor 0.35-μm technology. The pixel circuitry dissipates 15 μW at 3.3 V, has a noise equivalent charge of 82 e-rms at 200 fF, and allows, on each of the three channels, a dynamic range that exceeds 12 bits. The designed pixel is a square with a 109-μm pitch. [ABSTRACT FROM AUTHOR]

A novel approach to the design of high-performance operational-amplifier-based differential charge and transresistance amplifiers is proposed. It is based on a two-stage topology: The first stage performs a differential measurement to single-ended signal conversion, providing a common-mode rejection that only depends on the matching between two resistors; the second stage filters the signal. Three novel topologies that are based on this technique are presented, analyzed, and measured, and design criteria are finally given. Their performance is compared with that of a state-of-the-art topology that is used as the benchmark, and it results in a better common-mode rejection ratio (CMRR). [ABSTRACT FROM AUTHOR]

Abstract: To take advantage of the very low source emittance of third generation radiation sources high-resolution in situ X-ray beam monitors are required in order to keep the X-ray beam focussed and incident on the sample. We present a compact device based on a linear photodiode array. It consists of relatively few diodes that measure the spatially resolved scattered X-rays from a thin polymer foil placed in the beam path. The device is vacuum compatible, inexpensive and radiation hard. The scattered X-rays are incident on a strip of photodiodes that are connected to a dedicated multi-channel charge-sensitive read-out chip. Test experiments performed at the European Synchrotron Radiation Facility (ESRF) show, that even at a relatively low-intensity bending magnet beam line, X-ray beam position and profiles are obtained extremely fast and precise. [Copyright &y& Elsevier]

The optimization of the input MOSFET for charge amplifiers in deep submicron technologies is discussed. After a review of the traditional approach, the impact of properly modeling the equivalent series noise and gate capacitance of the MOSFET is presented. It is shown that the enhanced MOSFET model, when compared to the classical, produces a different resolution estimate and input MOSFET optimization result. The minimum channel length and the maximum allocated power are not always the best choice in terms of resolution. Also, in an optimized front-end, the low frequency noise contribution to the Equivalent Noise Charge may depend on the time constant of the filter. As an example, results from the commercial TSMC 0.25 mum CMOS technology are reported [ABSTRACT FROM PUBLISHER]

This paper presents the performance of a two-chip detector system based on a silicon drift detector and on a charge amplifier, part of the latter being integrated in the detector chip. The two-chip system is intended for high-resolution X-ray spectroscopy experiments in which stability of operation is mandatory to avoid on-line calibration procedures. Experimental measurements have been carried out to test the stability of the whole system with a quantitative analysis of the gain stability obtained by comparing X-ray spectra taken at different operating conditions, varying the temperature and/or the detector bias. A gain variation of less than 0.4% has been obtained at extreme operating conditions. The problems and critical aspects of the two-chip charge amplifier solution are discussed. [Copyright &y& Elsevier]