Charge Sensitive Amplifier Research Articles

Photon Counting Imaging with Low Noise and a Wide Dynamic Range for Aurora Observations.

The radiation intensity of observed auroras in the far-ultraviolet (FUV) band varies dramatically with location for aerospace applications, requiring a photon counting imaging apparatus with a wide dynamic range. However, combining high spatial resolution imaging with high event rates is technically challenging. We developed an FUV photon counting imaging system for aurora observation. Our system mainly consists of a microchannel plate (MCP) stack readout using a wedge strip anode (WSA) with charge induction and high-speed electronics, such as a charge sensitive amplifier (CSA) and pulse shaper. Moreover, we constructed an anode readout model and a time response model for readout circuits to investigate the counting error in high counting rate applications. This system supports global rates of 500 kilo counts, 0.610 dark counts s−1 cm−2 at an ambient temperature of 300 K and 111 µm spatial resolution at 400 kilo counts s−1 (kcps). We demonstrate an obvious photon count loss at incident intensities close to the counting capacity of the system. To preserve image quality, the response time should be improved and some noise performance may be sacrificed. Finally, we also describe the correlation between counting rate and imaging resolution, which further guides the design of space observation instruments.

Low-energy X-ray performance of SOI pixel sensors for astronomy, “XRPIX”

We have been developing a new type of X-ray pixel sensors, “XRPIX”, allowing us to perform imaging spectroscopy in the wide energy band of 1–20keV for the future Japanese X-ray satellite “FORCE”. The XRPIX devices are fabricated with complementary metal-oxide-semiconductor silicon-on-insulator technology, and have the “Event-Driven readout mode”, in which only a hit event is read out by using hit information from a trigger output function equipped with each pixel. This paper reports on the low-energy X-ray performance of the “XRPIX6E” device with a Pinned Depleted Diode (PDD) structure. The PDD structure especially reduces the readout noise, and hence is expected to largely improve the quantum efficiencies for low-energy X-rays. While F-K X-rays at 0.68keV and Al-K X-rays at 1.5keV are successfully detected in the “Frame readout mode”, in which all pixels are read out serially without using the trigger output function, the device is able to detect Al-K X-rays, but not F-K X-rays in the Event-Driven readout mode. Non-uniformity is observed in the counts maps of Al-K X-rays in the Event-Driven readout mode, which is due to region-to-region variation of the pedestal voltages at the input to the comparator circuit. The lowest available threshold energy is 1.1keV for a small region in the device where the non-uniformity is minimized. The noise of the charge sensitive amplifier at the sense node and the noise related to the trigger output function are ∼18e− (rms) and ∼13e− (rms), respectively.

Design and optimization of the CSA-based readout electronics for STCF ECAL

In this paper, a front-end electronics system based on charge sensitive amplifier (CSA) is designed to read out the signal of pure CsI (pCsI) crystal, which is the basic option of Super Tau-Charm Facility (STCF) electromagnetic calorimeter (ECAL). By noise analysis and on-board testing, parameters of the readout circuit are optimized. Thus the noise of the system with large input capacitance of avalanche photodiode (APD) is significantly reduced. A noise level of 675 electrons for electronics alone and 1025 electrons with S8664-0505 APD is realized, which satisfies the project requirements.

Investigation of ASIC-based signal readout electronics for LEGEND-1000

LEGEND, the Large Enriched Germanium Experiment for Neutrinoless ββ Decay, is a ton-scale experimental program to search for neutrinoless double beta (0νββ) decay in the isotope 76Ge with an unprecedented sensitivity. Building on the success of the low-background 76Ge-based GERDA and \ extsc{Majorana Demonstrator} experiments, the LEGEND collaboration is targeting a signal discovery sensitivity beyond 1028 yr on the decay half-life with approximately 10 t⋅yr of exposure. Signal readout electronics in close proximity to the detectors plays a major role in maximizing the experiment's discovery sensitivity by reducing electronic noise and improving pulse shape analysis capabilities for the rejection of backgrounds. However, the proximity also poses unique challenges for the radiopurity of the electronics. Application-specific integrated circuit (ASIC) technology allows the implementation of the entire charge sensitive amplifier (CSA) into a single low-mass chip while improving the electronic noise and reducing the power consumption. In this work, we investigated the properties and electronic performance of a commercially available ASIC CSA, the XGLab CUBE preamplifier, together with a p-type point contact high-purity germanium detector. We show that low noise levels and excellent energy resolutions can be obtained with this readout. Moreover, we demonstrate the viability of pulse shape discrimination techniques for reducing background events.

SliT: A Strip-Sensor Readout Chip With Subnanosecond Time Walk for the J-PARC Muon g − 2/EDM Experiment

A new silicon-strip readout chip named "SliT" has been developed for the measurement of the muon anomalous magnetic moment and electric dipole moment at J-PARC. The SliT is designed in the Silterra 180 nm CMOS technology with mixed-signal integrated circuits. An analog circuit incorporates a conventional charge-sensitive amplifier, shaping amplifiers, and two distinct discriminators for each of 128 identical channels. A digital part includes storage memories, an event building block, a serializer, and LVDS drivers. A distinct feature of the SliT is utilization of the zero-cross architecture, which consists of a CR-RC filter followed by a CR circuit as a voltage differentiator. This architecture enables to generate hit signals with subnanosecond amplitude-independent time walk, which is the primary requirement for the experiment. The test results show the time walk of $0.38 \pm 0.16$ ns between 0.5 and 3 MIP signals. The equivalent noise charge is $1547 \pm 75 $ $e^{-}$ (rms) at $C_{\rm det} = 33$ pF as a strip-sensor capacitance. Other functionalities such as a strip-sensor readout chip have also been proven in the tests. The SliT128C satisfies all requirements of the J-PARC muon $g-2$/EDM experiment.

Topmetal-M: A novel pixel sensor for compact tracking applications

The Topmetal-M is a large area pixel sensor (18 mm × 23 mm) prototype fabricated in a new 130 nm high-resistivity CMOS process in 2019. It contains 400 rows × 512 columns square pixels with the pitch of 40μm. In Topmetal-M, a novel charge collection method combining the Monolithic Active Pixel Sensor (MAPS) and the Topmetal sensor has been proposed for the first time. Both the ionized charge deposited by the particle in the sensor and along the track over the sensor can be collected. The in-pixel circuit mainly consists of a low-noise charge sensitive amplifier to establish the signal for the energy reconstruction, and a discriminator with a Time-to-Amplitude Converter (TAC) for the Time of Arrival (TOA) measurement. With this mechanism, the trajectory, particle hit position, energy, and arrival time of the particle can be measured. The analog signal from each pixel is accessible through time-shared multiplexing over the entire pixel array. This paper will discuss the design and preliminary test results of the Topmetal-M sensor.

Radiation-Hardened Sensor Interface Circuit for Monitoring Severe Accidents in Nuclear Power Plants

Radiation sensor interface circuits can be mounted on sensor nodes in wireless sensor networks to detect radiation signals. They respond quickly to operators and command centers, allowing appropriate decisions to be made to mitigate nuclear power plant accidents. For instance, high-level radiation leaked from a reactor building during a nuclear plant accident can degrade the performance of the radiation sensor interface implemented by integrated circuits due to threshold voltage shift, leakage current change, and noise increase induced by radiation impact events. To obtain reliable signal measurements in the high radiation environment, radiation-hardening technologies must be applied to radiation sensor interface circuits. The radiation-hardened sensor interface circuit proposed in this article exploits a pair of charge-sensitive amplifiers (CSAs) in dual paths to equivalently cancel out the distorted output signals caused by radiation impacts on the circuits. In addition, a low-power, fully differential successive approximation register (SAR) analog-to-digital converter (ADC) is used to reduce the radiation effects by subtracting the radiation-induced noise of one input from the other. The implemented radiation sensor interface circuit can maintain its performance up to 1.0 mrad (SiO2) of irradiation with only 2.5 mW power consumption, while successfully sensing and transferring the radiation information to the downstream signal-processing network.

TERA: Throughput-Enhanced Readout ASIC for High-Rate Energy-Dispersive X-Ray Detection

This work presents throughput-enhanced readout ASIC (TERA), an integrated multichannel analog pulse processor (APP), suitable for processing signals generated from solid-state detectors, such as silicon drift detectors (SDDs) coupled to pulsed reset-type charge-sensitive amplifiers (CSAs). In particular, this development targets applications at high count rates (≈Mcps) in energy-dispersive X-ray spectroscopy. The demonstrator chip is composed of four parallel readout channels. Each channel includes a seventh-order semi-Gaussian shaping amplifier with controllable shaping times and full-scale ranges, followed by a peak stretcher and switched-capacitor analog memory. Each channel is also equipped with a dedicated peak detector and a novel pile-up rejection (PUR) logic. Each pair of channels can be optionally digitized by a 12-bit on-chip successive-approximation-register (SAR) analog-to-digital converter (ADC), providing a digital output at a maximum sampling rate of 2.5 Msps. The architecture achieves high throughput and satisfactory energy resolution. In fact, in 55Fe spectroscopy measurements, when using the shortest shaping pulsewidth of 200 ns, a full-width at half-maximum (FWHM) Mn $\text{K}\alpha $ line of 159.4 eV (12.5 $\text{e}^{-}_{\text {rms}}$ ) was obtained at low rates (10 kcps). This energy resolution can be achieved, thanks to the minimization of the effect of the ballistic deficit, achieved by optimizing the SDD detector in terms of optimum biasing, low operating temperature (−37 °C), and small size (1-mm diameter). At 1.61 Mcps/channel input rate, an output count rate of 1.09 Mcps/channel and a resolution of 205.1 eV (19.7 $\text{e}^{-}_{\text {rms}}$ ) were achieved with a 4-mm-diameter SDD and optimum PUR settings. Simultaneous multichannel acquisition has been successfully performed. Such high-rate performances are, to our knowledge, the best ones reported so far for an APP, based on a spectroscopy-grade application-specific integrated circuit (ASIC), and very close to those achievable by a standard digital pulse processor (DPP). Therefore, TERA can represent an attractive, compact, and scalable pulse processing solution for high-rate multichannel energy-dispersive X-ray detection systems.

Analysis of the results of designing reading electronics of silicon photomultiplier tubes driven by the base matrix crystal MN2XA030

The aim of the work is analyzing the results of an experimental research of a charge-sensitive amplifier with an adjustable conversion coefficient and a base level recovery circuit fabricated on the master slice array MN2XA030 for silicon photomultiplier tubes. The amplifier is called ADPreampl3. The parameters were measured on a small batch of chips in the amount of 20 samples. In the process of measuring the main parameters of the amplifier, the signal from the SiPM Photonique equivalent circuit was fed to the amplifier input. In the course of measuring the parameters, it was revealed that the spread of the baseline level for the FOut output ranged from -24 to 276 mV with an average value of 85.6 mV. In this case, a voltage changing in the FOoutShift node from -3 to 3 V is sufficient to establish a base level value of FOut output close to zero. When the recovery scheme is disabled, the spread of the basic level for OutA output is from 300 to 800 mV. When the OutAShift output is connected to the zero-voltage bus the average base level for OutA output is 3.72 mV and for OutAinv output it is minus 2.42 mV. The base level at the outputs OutA and OutAinv smoothly changes in the range of ± 0.9 V. At maximum gain, the dynamic range of ADPreampl3 exceeds 20 dB, however, at the same time, the conversion coefficient depends on the value of the input charge. To register large input charges, it is recommended to reduce the output pulse by reducing the voltage at the Gain pin or process the signal from the FOut pin. The output parameters of the experimental samples are compared with the results of computer simulation. The discrepancy between the results of modeling and measurements, peak time and propagation delays of the amplifier signal was revealed. Based on this, a decision to adjust the SPICE parameters of the elements used in the simulation was made.

Integrated Circuit Design for Radiation-Hardened Charge-Sensitive Amplifier Survived up to 2 Mrad.

According to the continuous development of metal-oxide semiconductor (MOS) fabrication technology, transistors have naturally become more radiation-tolerant through steadily decreasing gate-oxide thickness, increasing the tunneling probability between gate-oxide and channel. Unfortunately, despite this radiation-hardened property of developed transistors, the field of nuclear power plants (NPPs) requires even higher radiation hardness levels. Particularly, total ionizing dose (TID) of approximately 1 Mrad could be required for readout circuitry under severe accident conditions with 100 Mrad around a reactor in-core required. In harsh radiating environments such as NPPs, sensors such as micro-pocket-fission detectors (MPFD) would be a promising technology to be operated for detecting neutrons in reactor cores. For those sensors, readout circuits should be fundamentally placed close to sensing devices for minimizing signal interferences and white noise. Therefore, radiation hardening ability is necessary for the circuits under high radiation environments. This paper presents various integrated circuit designs for a radiation hardened charge-sensitive amplifier (CSA) by using SiGe 130 nm and Si 180 nm fabrication processes with different channel widths and transistor types of complementary metal-oxide-semiconductor (CMOS) and bipolar CMOS (BiCMOS). These circuits were tested under γ–ray environment with Cobalt-60 of high level activity: 490 kCi. The experiment results indicate amplitude degradation of 2.85%–34.3%, fall time increase of 201–1730 ns, as well as a signal-to-noise ratio (SNR) of 0.07–11.6 dB decrease with irradiation dose increase. These results can provide design guidelines for radiation hardening operational amplifiers in terms of transistor sizes and structures.

Reducing noises of high-speed Bi-JFET charge-sensitive amplifiers during schematic design

The technique of circuit noise reduction of charge-sensitive amplifiers containing bipolar and junction field-effect transistors is considered. The initial and improved circuit of the integrated charge-sensitive amplifiers using the above mentioned technique, the results of the step-by-step noise reduction when changing the sizes and operating modes of transistors, and improvement of the bias circuits are presented.

Dynamic Calibration Enables High-Accuracy Charge Measurements on Individual Ions for Charge Detection Mass Spectrometry.

Charge detection mass spectrometry (CDMS) depends on the measurement of the charge induced on a cylinder by individual ions by means of a charge-sensitive amplifier. For high-accuracy charge measurements, the detection cylinder is embedded in an electrostatic linear ion trap (ELIT), and the ions oscillate back and forth through the cylinder so that multiple measurements are made. To assign the charge state with a low error rate, the charge of each ion must be determined with an uncertainty (root-mean-square deviation) of around 0.2 elementary charges. We show here that high-accuracy charge measurements can be achieved for large ions by dynamic calibration of the charge measurement using an internal standard. The internal standard is generated by irradiating the detection cylinder, by means of a small antenna, with a radiofrequency signal. Using this approach, we have obtained a relative charge uncertainty of around 5 × 10-4, allowing charge-state resolution to be achieved for single ions with up to 500 charges. In another application of this approach, the detection cylinder is irradiated with a signal that counteracts the transients generated when the potentials on the ELIT end-caps are switched to trapping mode. Using this approach, the dead time after switching (during which the signal cannot be analyzed) has been reduced by more than an order of magnitude. With charge-state resolution for ions with up to 500 charges, we were able to calibrate the charges precisely. The results show that the response of the charge-sensitive amplifier with dynamic calibration is linear to within a small fraction of an elementary charge.

A 0.35μm Low-Noise Stable Charge Sensitive Amplifier for Silicon Detectors Applications

The Charge Sensitive Amplifier (CSA) is the key module of the front-end electronics of various types of Silicon detectors and most radiation detection systems. High gain, stability, and low input noise are the major concerns of a typical CSA circuit in order to achieve amplified susceptible input charge (current) for further processing. To design such a low-noise, stable, and low power dissipation solution, a CSA is required to be realized a complementary metal-oxide-semiconductor (CMOS) technology with a compact design. This research reports a low-noise highly stabile CSA design considerations for Silicon detectors applications, which has been designed and validated in TSMC 0.35um CMOS process. In a typical CSA design, the detector capacitance and the input transistor’s width are the most dominating parameters for achieving low noise performance. Therefore, the Equivalent Noise Charge (ENC) with respect to those parameters has been optimized, for a set of detector capacitance from 0.2pF – 2pF. However, the parallel noise of the feedback was removed by adopting a voltage-controlled NMOS resistor, which in turn helped to achieve high stability of the circuit. The simulation results provided a baseline gain of 9.92mV/fC and show that ENC was found to be 42.5e – with 3.72 e – /pF noise slope. The Corner frequency exhibited by the CSA is 1.023GHz and the output magnitude was controlled at -56.8dB; it dissipates 0.23mW from with a single voltage supply of 3.3V with an active die area of 0.0049 mm 2 .

High throughput rate digital processor based on real-time current pulse analysis

Charge sensitive type preamplifiers are usually used in scintillators, such as NaI (TI) and BGO, to preprocess the current pulse output of detectors. Under high-intensity gamma radioactive field, the wide falling edge of a charge sensitive preamplifier signal will cause a serious pulse pile-up, and the pile-up pulse will be discarded. Consequently, the pulse throughput rate declines significantly. Meanwhile, the charge sensitive amplifier can easily integrate two pulses with an approximate time of arrival into a single pulse to generate an accidental coincidence effect. After using a current-sensitive amplifier on the current pulse output from the detector in the system designed in this work, such output is digitalized by using a waveform digitizer with 125MHz sampling rate. The baseline is estimated statistically via a histogram, a real-time fitting and peeling algorithm is designed for the falling edge pile-up of the current pulse signal to recover the pile-up signal, and the digital charge of the current pulse signal is integrated to obtain particle energy. A 4L NaI(TI) scintillator detector is used in the experiment to measure the 137Cs γ radioactive source. Under a 165kcps counting rate, the pulse throughput rate is up to 99 %, the accidental coincidence probability is 0.387%, and the energy resolution reaches 7.54%, Even under a 3Mcps counting rate, the pulse throughput rate is still 85.43%. Therefore, the overall performance is superior to conventional voltage-type digital spectrometers under high counting rate application.

A 4-MHz, 256-Channel Readout ASIC for Column-Parallel CCDs With 78.7-dB Dynamic Range

A 256-channel readout application specific integrated circuit (ASIC) called the very low-noise analog sampling engine (VASE) intended for the readout of column-parallel charge-coupled devices (CP-CCDs), is presented. Each channel uses a charge-sensitive amplifier and a first-order dual-gain sigma-delta analog-to-digital converter (ADC) that act as the front end of an extended counting ADC. The extended counting ADC directly implements correlated multiple-sampling as part of its operation. To reduce the noise due to input capacitance and to ensure a compact camera, the VASE input bonding pads are pitch matched to the CP-CCD to allow chip-to-chip bonding with minimal parasitic capacitance. The chip is designed in a modular way with each 16 input channels sharing a single differential analog output and digital serializer. VASE, with a die area of 38.1 mm2 and fabricated in 180-nm CMOS technology, achieves 22 e− equivalent noise charge (ENC) and a dynamic range of 190 ke− (78.7 dB) at a 4-MHz pixel rate (corresponding to a frame rate of 32 kfps when a $256\times256$ pixel sensor is read out on both sides) while dissipating 10.1 mW per channel. The prototype has been used to successfully image X-ray diffraction at a soft X-ray synchrotron.

Charged Particle Pickup Tube Detector Used in Experimental Applications and Classroom Demonstrations

Acharge pickup detector was developed at the University of Colorado for use in classroom demonstrations and in the dust accelerator at the Institute for Modeling Plasma, Atmospheres and Cosmic Dust (IMPACT). The detector can be used in a physics classroom to help high school and introductory-level physics students connect electromagnetic phenomena with measurement techniques that are common to experimental physics and in electronics courses to demonstrate the use of a charge-sensitive amplifier (CSA). Construction of a similar detector would develop students’ basic machining and electronics skills, which are crucial in most undergraduate experimental physics opportunities. The detector is designed to nondestructively determine the velocity and charge of particles. The detector is compact (8.6 cm x 5.4 cm x 4.1 cm), simple, and lightweight. It is built with off-the-shelf components with simple machining, resulting in a low-cost (∼$100) detector that maintains the high sensitivity (0.2 fC) necessary for characterization of most hypervelocity dust particles, as well as a wide variety of other applications accessible to introductory-level physics students such as charged particles in a dust storm, pith balls, or charged raindrops. This paper focuses on both characterization of the detector using the accelerator at IMPACT and the basics of the undergraduate-level physics principles, electronics principles, mechanical design, and lab applications.

Miniaturized 0.13-μm CMOS Front-End Analog for AlN PMUT Arrays.

This paper presents an analog front-end transceiver for an ultrasound imaging system based on a high-voltage (HV) transmitter, a low-noise front-end amplifier (RX), and a complementary-metal-oxide-semiconductor, aluminum nitride, piezoelectric micromachined ultrasonic transducer (CMOS-AlN-PMUT). The system was designed using the 0.13-μm Silterra CMOS process and the MEMS-on-CMOS platform, which allowed for the implementation of an AlN PMUT on top of the CMOS-integrated circuit. The HV transmitter drives a column of six 80-μm-square PMUTs excited with 32 V in order to generate enough acoustic pressure at a 2.1-mm axial distance. On the reception side, another six 80-μm-square PMUT columns convert the received echo into an electric charge that is amplified by the receiver front-end amplifier. A comparative analysis between a voltage front-end amplifier (VA) based on capacitive integration and a charge-sensitive front-end amplifier (CSA) is presented. Electrical and acoustic experiments successfully demonstrated the functionality of the designed low-power analog front-end circuitry, which outperformed a state-of-the art front-end application-specific integrated circuit (ASIC) in terms of power consumption, noise performance, and area.

Design and testing of a miniature silicon strip detector

In this study, we developed a multi-channel low-noise electronic readout system for a silicon strip detector. Using two charge-sensitive amplifier VA140 chips from IDEAS in Norway, the system has a wide linear dynamic input range of up to 180 fC for 128 channels with 0.16 fC average equivalent noise charge. In addition, we studied the charge distribution behaviors between adjacent silicon strips with the help of transient current technology.

Implementation of a Charge-Sensitive Amplifier without a Feedback Resistor for Charge Detection Mass Spectrometry Reduces Noise and Enables Detection of Individual Ions Carrying a Single Charge.

Charge detection mass spectrometry (CDMS) depends on the measurement of the charge induced on a cylinder by individual ions by means of a charge-sensitive amplifier. Electrical noise limits the accuracy of the charge measurement and the smallest charge that can be detected. Thermal noise in the feedback resistor is a major source of electrical noise. We describe the implementation of a charge-sensitive amplifier without a feedback resistor. The design has significantly reduced 1/f noise facilitating the detection of high m/z ions and substantially reducing the measurement time required to achieve almost perfect charge accuracy. With the new design we have been able to detect individual ions carrying a single charge. This is an important milestone in the development of CDMS.

Development of charge sensitive amplifiers based on various circuit board substrates and evaluation of radiation hardness characteristics

Ultra-low noise charge sensitive amplifiers (CSAs) based on various types of circuit board substrates, such as FR4, Teflon, and ceramics (Al2O3) with two different designs, PA1 and PA2, have been developed. They were tested to see the noise effect from the dielectric loss of the substrate capacitance before and after irradiation. If the electronic noise from the CSAs is to be minimized and the energy resolution enhanced, the shaping time has to be optimized for the detector, and a small feedback capacitance of the CSA is favorable for a better SNR. Teflon- and ceramic-based PA1 design CSAs showed better noise performance than the FR4-based one, but the Teflon-based PA1 design showed better sensitivity than ceramic based one at a low detector capacitance (<10 pF). In the PA2 design, the equivalent noise and the sensitivity were 0.52 keV FWHM for a silicon detector and 7.2 mV/fC, respectively, with 2 μs peaking time and 0.1 pF detector capacitance. After 10, 100, 103, 104, and 105 Gy irradiation the ENC and sensitivity characteristics of the developed CSAs based on three different substrate materials are also discussed.