Low-noise Preamplifier Research Articles

Miniaturized preamplifier integration in ultrasound transducer design for enhanced photoacoustic imaging.

Photoacoustic imaging (PAI) utilizes the photoacoustic effect to record both vascular and functional characteristics of a biological tissue. Photoacoustic signals have typically low amplitude that cannot be read efficiently by data acquisition systems. This necessitates the use of one or more amplifiers. These amplifiers are somewhat bulky (e.g., the ZFL-500LN+, Mini-Circuits, USA, or 351A-3-50-NI, Analog Modules Inc., USA). Here, we describe the fabrication and development process of a transducer with a built-in low-noise preamplifier that is encased within the transducer housing. This new, to the best of our knowledge, design could be advantageous for applications where a compact transducer + preamplifier is required. We demonstrate the performance of this compact detection unit in a laser scanning photoacoustic microscopy system by imaging a rat ear ex vivo and a rat brain vasculature in vivo.

Design and Testing of a Fast-Response Preamplifier

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

A low noise and wide dynamic range preamplifier for HPGe detectors

A low noise and wide dynamic range preamplifier for HPGe detectors

Photomultiplier Tubes for Programmable Logic Controller Foreign Object Sorting System and Its Performance Analysis

The photoelectric foreign object sorting system is a comprehensive device developed to remove foreign objects from target substances, integrating photoelectric, computer, and mechanical technologies. This system combines photoelectric, computer image, and mechanical technologies to identify materials based on color and appearance, utilizing the scattered light returned from the scanned object for detection and recognition. This work designs a photoelectric foreign object sorting system for food and tobacco. This system takes photomultiplier tubes as the main photoelectric devices and a programmable logic controller (PLC) as the control unit. The hardware components of this system include the design of a low-noise preamplifier, conditioning circuit, ADC data acquisition module, and PLC-external circuit connections. In simulation experiments, testing is conducted on the low-noise preamplifier, considering the significant impact of the collected signals on subsequent analysis. Amplitude-frequency and phase-frequency tests show that the circuit signal output of this module is stable. There are no oscillations in the time domain, and no occurrences of overshooting or ringing in frequency. The noise indicates that the signal noise of this module is relatively low. During the debugging process, ADA4896 is selected, and a black-and-white alternating stripe with a 3 mm spacing is used as the scanning object. As expected, the first-stage amplification results of the low-noise preamplifier show a range of 2 mV with some DC components in the output voltage. In its second-stage amplification, the fine scale reaches 10 mV, and the output signal can represent the physical characteristics of the scanned object.

Dual-Stage Double-Pass Extended L-Band Erbium-Doped Fiber Amplifier with Improved Gain Performance

Extended L-band erbium-doped fiber amplifiers (EDFAs) have attracted much attention in recent years despite their relatively low gain levels. In this paper, a dual-stage extended L-band EDFA with improved gain level is demonstrated by using an Er/Yb/P co-doped fiber-based double-pass structure assisted by a low noise pre-amplifier. High gain levels of up to 48.79 dB at 1566 nm and 20.05 dB at 1621.4 nm are achieved with saturated output power at 1605 nm of 20.58 dBm under a total pump power of only 400 mW. Bandwidths with the gain of more than 20 and 30 dB are reached up to 66 nm (1555.4–1621.4 nm) and 58.4 nm (1557.5–1615.9 nm), respectively. The noise figure benefited by using the low noise pre-amplifier is 5.40 ± 1.55 dB in the 1565–1610 nm range. The wide gain bandwidth, high gain level and relatively low pump power give it great potential for future high-capacity optical fiber communication systems.

Design and performance of a high-speed and low-noise preamplifier for SiPM

Design and performance of a high-speed and low-noise preamplifier for SiPM

Electron Temperature Measurements Using a Two-Filter Soft X-ray Array in VEST.

A multichannel soft X-ray (SXR) array has been developed to measure the electron temperature in the Versatile Experiment Spherical Torus (VEST). To estimate electron temperature using the two-filter method applied to SXR intensity, we designed a pinhole camera that has two photodiode arrays with different metallic filters. We also adopted a filter wheel and tested various filter parameters to find the optimal filter set. Through tests, the combination of aluminum and beryllium was found to be the most suitable for the current experimental conditions in VEST. The filtered SXR signals were acquired with a low-noise preamplifier, exhibiting sufficient signal-to-noise ratios for electron temperature estimation based on the intensity ratio of two signals obtained with different filters. The estimated electron temperature from the developed two-filter SXR array showed reasonably matched levels and consistent trends with Thomson scattering measurements. Error contribution from impurity line emission is also discussed.

A flexible 8.5 MHz litz wire receive array for field-cycling imaging

Objectives. Low frequency coils present unique challenges as loop losses, component losses, and the supporting electronics can significantly degrade the signal-to-noise ratio (SNR). SNR may already be a limiting factor with MRI at low field (and frequency), therefore the minimization of additional loss is particularly important. If interactions between loops are managed, array coils can provide increased SNR, coverage, and potentially imaging speed. In this work, we investigate methods to characterise and preserve SNR from a low frequency coil array, allowing a more geometrically conforming array for quick, no-tune application with various anatomies. Approach. Single and multi-turn, 16.2 cm diameter litz wire loops were constructed and characterised for losses under various loading conditions. Low noise preamplifiers were acquired and characterized, as well as interfacing electronics were developed and evaluated. A bench level SNR test was implemented to observe the effects of tuning and loading on individual coils. The results were used to select a design for construction of a 6-channel, flex array coil. Main results. Ultra fine strand litz wire exhibited lower losses than equivalent diameter solid wire which should translate to improved SNR and provides the mechanical flexibility needed in a conforming array. Single turn loop losses were dominant under all loading conditions; however, 2 and 3 turn loops were body loss dominated under modest loading conditions. Preamplifier blocking achieved was well short of our design goal and critical overlaps became necessary for coil-to-coil interaction control. Our finished array, a 3-channel posterior array coil and a 3-channel anterior array coil, conforms nicely to various anatomies and is providing consistent results in various volunteer study trials. Significance. Receive coils are challenging at low fields as loop losses often limit the final SNR. This is exacerbated in an array coil as loops may be smaller and not coupled well to the body. In this work we have demonstrated that body loss dominance is possible with 16.2 cm loops at 8.5 MHz. We have optimized, built, and tested low noise interfacing electronics and characterized the SNR penalties as the tuning and loading is varied, a key parameter in a geometrically flexible array designed for rapid setup. The resultant 6-channel, general-purpose array is supporting various Field-Cycling Imaging studies where body habitus and anatomies require a flexible, adaptable array coil which can be quickly positioned and utilized.

A low-noise current-sensitive preamplifier VIEC based on a charge-sensitive preamplifier

A low-noise current-sensitive preamplifier VIEC has been developed based on the circuitry of a charge-sensitive preamplifier. In this paper, the dynamic ranges of the VIEC and a conventional current-sensitive preamplifier are measured and compared. A method to increase the dynamic range of the VIEC is described. Using the VIEC with enhanced dynamic range, a computed tomography measurement is performed for a strongly attenuating phantom comprising a 10-cm-diameter acrylic cylinder with a 3-cm-diameter iron rod in the center. • Low noise current preamplifier VIEC showed wide dynamic range. • Further enlargement of the dynamic range of the VIEC is proposed and demonstrated. • Computed tomography image and profile of a strongly attenuating phantom are shown.

SECALROC2: A Low-Noise, High-Speed, and Full Digital Outputs Front-End ASIC for STCF Electromagnetic Calorimeter With APD Detectors

In this work, a low-noise and high-rate front-end readout application-specific integrated circuit (ASIC) named SECALROC2 for the electromagnetic calorimeter (ECAL) in the super tau-charm factory (STCF) is presented. The chip is designed to process signals generated from avalanche photodiode detectors (APDs) for both energy and time measurement. The large detector capacitance and leakage current of the APD pose a great challenge to the noise and speed performance of the front-end readout circuit (ROC). A low-noise preamplifier and a fifth-order high-linearity shaper with adjustable peaking times are proposed to decrease noise induced by the 270-pF detector capacitance. A peak detect-and-hold circuit and a high-linearity differential analog buffer are adopted to convert each peak voltage of the shaper to differential voltages with sufficient driving capability. A fast shaper and a discriminator are implemented to produce trigger signals for the time of arrival (TOA) measurement. To reduce the complexity and power consumption of the ECAL system, a 12-bit 10-MS/s pipelined analog-to-digital converter (ADC) and a 16-bit three-stage time-to-digital converter (TDC) with 42-ps bin size TDC are integrated on-chip for full-digitalized outputs. This ASIC was designed and fabricated in a standard commercial 1P6M 0.18- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> mixed-signal CMOS process and the chip area occupancy is <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2.4\times1.6$ </tex-math></inline-formula> mm2. The experimental results show that the input charge of the ASIC ranges from 3.2 to 400 fC. The measured nonlinear error of the system is less than 2.5% with an event rate up to 400 kcps. The equivalent noise charge (ENC) is 1367 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{e}^{-}$ </tex-math></inline-formula> + 4.93 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{e}^{-}$ </tex-math></inline-formula> /pF at 800-ns peaking time. The timing resolution is better than 540 ps at an input charge of 160 fC. The measured ENC can achieve 3820 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{e}^{-}$ </tex-math></inline-formula> when the ASIC is connected to an APD detector. The effective number of bits (ENOB) of the ADC is 10.8-bit when operated at 10 MS/s.

Compound Preselector for Multistatic Passive Radar Employed in Remote Sensing Applications

Passive radars and multistatic passive radars in particular are gaining increasing attention. It is due to their effectiveness in detecting, tracking and identifying targets. Multistatic passive radars are used in remote sensing observations of the Earth’s ionosphere, meteors, space junk, etc. Another application is the detection and tracking of manmade objects and vehicles in the atmosphere or on the surface of the Earth. The current paper discusses a hardware design approach applicable to the front-end of a multistatic passive radar receiver, namely a compound preselector. The preselector is a very important part of the radio receiver in cases where there are strong neighbouring signals in the radio band of operation. Such strong signals may overload the receiver or the low noise preamplifier and render the whole system dysfunctional. This article elaborates on a two-component preselector having very high rejection ratio to nearby emitters, still keeping the receiver simple and reliable. The authors have registered several utility models on innovations in multistatic passive radars at Patent Office of Republic of Bulgaria.

HKROC: an integrated front-end ASIC to readout photomultiplier tubes for the Hyper-Kamiokande experiment

The HKROC ASIC was originally designed to readout the photomultiplier tubes (PMTs) for the Hyper-Kamiokande (HK) experiment. HKROC is a very innovative ASIC capable of readout a large number of channels satisfying stringent requirements in terms of noise, speed and dynamic range. Each HKROC channel features a low-noise preamplifier and shapers, a 10-bit successive approximation Analog-to-Digital Converter (SAR-ADC) (designed by AGH Krakow) for the charge measurement (up to 2500 pC) and a Time-to-Digital Converter (TDC) (designed by CEA IRFU group) for the Time-of-Arrival (ToA) measurement with 25 ps binning. HKROC is auto-triggered and includes all necessary ancillary services as bandgap circuit, PLL (Phase-locked loop) and threshold DACs (Digital to Analog Converters). This paper will describe the ASIC architecture and the experimental results of the first HKROC prototype received in January 2022.

Charge sensitive preamplifier design optimization for low-pressure Micro-Megas gaseous detector operations

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.

HGCROC2: the front-end readout ASICs for the CMS High Granularity Calorimeter

The CMS High-Granularity Calorimeter (HGCAL) imposes extremely challenging specifications for the front-end electronics: high dynamic range, low noise, high-precision time information and low power consumption, as well as the need to select and transmit trigger information with a high transverse and longitudinal granularity. HGCROC2 is the second prototype of the readout chip embedding almost all the final functionalities. It has 72 channels of the full analog chain: low noise and high gain preamplifier and shapers, a 10-bit 40 MHz SAR-ADC which provides the charge measurement over the linear range of the preamplifier, after the preamplifier saturation a discriminator and TDC provide the charge information from ToT (200 ns dynamic range and 50 ps binning), and a fast discriminator and TDC provide timing information to 25 ps accuracy. This paper reports on the performance in terms of noise, charge and timing, the DAQ and Trigger paths, as well as results from radiation qualification with total ionizing dose (TID) and heavy ions for single-event effects (SEE).

Integrated 2D beam emission spectroscopy diagnostic at the Huan-Liuqi-2A (HL-2A) tokamak.

Two newly developed, eight-channel, integrated Beam Emission Spectroscopy (BES) detectors have been installed at Huan-Liuqi-2A tokamak, which extends the existing 16 single-channel modular BES system with additional 16 spatial channels. The BES collects the Doppler-shifted Balmer Dα emission with a spatial resolution of 1cm (radial) × 1.5cm (poloidal) and a temporal resolution of 0.5 µs to measure long-wavelength (k⊥ρi < 1) density fluctuations. Compared to the modular BES, the dark noise of the integrated BES is reduced by 50%-60% on average. The signal-to-noise ratio of the integrated BES system is optimized by the high light throughput front-end optics, high quantum efficiency photodiodes, high-gain, low-noise preamplifiers, and sufficient cooling capacity provided by the thermoelectric cooling (TEC) units that maintain the detectors at -20 °C. Crosstalk between channels that share the same optical system is found to be negligible. High-quality density fluctuation data enables 2D (radial-poloidal) imaging of turbulence, which allows for multi-channel spectral analysis, multi-channel cross-correlation analysis and velocimetry analysis. Preliminary results show that BES successfully captures the spatiotemporal features of the local turbulence and obtains statistically consistent turbulence characterization results.

Analysis and Optimization of Signal Detection Noise of Single-Beam Modulated Atomic Magnetometer Array

Highly sensitive atomic magnetometers (AMs) have been wildly used to form magnetocardiography (MCG) or magnetoencephalography (MEG) devices recently. However, signal detection noise, including light noise due to pump light fluctuations and electrical noise introduced by the detection circuit, will inevitably affect the sensitivity of the AM. Therefore, this article proposes a novel method to suppress signal detection noise and improve the sensitivity of AM. We first propose a low-noise preamplifier circuit to suppress the electrical noise of the signal detection part. Then, based on the equivalent magnetic noise amplitude, a method to optimize the pump light intensity is proposed. The experimental setup has been established. Both the analysis and experimental results can be evaluated that the magnetometer sensitivity can always be maintained at a relatively high-sensitivity level (around 24 fT/Hz <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{1/2}$ </tex-math></inline-formula> ) over a wide range of light intensities. We hope that the method proposed in this article can contribute to the improvement of sensor sensitivity in array AM systems.

A cryogenic low-background low-noise CMOS preamplifier for HPGe detectors

A cryogenic low-noise CMOS preamplifier has been successfully developed for HPGe detectors in low-background experiments. Commonly used auxiliary off-chip devices, such as decoupling capacitors and resistors, were removed to control the radioactive emission. The prototype chip was implemented in XFAB 350 nm CMOS process and was fully evaluated. A minimum ENC of 8.9 electrons was obtained at a 12 μs shaping time at 77 K, and the rise time was measured to be 60 ns through a 1-meter-long cable. The performances with and without decoupling capacitors for the power supply and bias voltages were compared, and there was no evident difference between these cases. The performance upon connection to a 0.5 kg point-contact HPGe detector was also measured. A minimum ENC of 15.5 electrons was achieved. The energy spectrum of the 57Co radiation source was obtained, and the FWHM of the 122 keV energy peak was measured to be 0.6 keV.

A compact magnetic resonance system with inside-out sensor for soil moisture measurement

Accurate measurement of soil moisture parameters plays a vital role in promoting agricultural production. Nuclear magnetic resonance (NMR) measuring instruments have become increasingly compact, especially in low field applications. However, NMR soil moisture measurement instruments still have problems with portability. We report on a compact NMR measuring instrument that focuses on the circuit’s design and construction. The instrument includes an inside-out sensor, NMR spectrometer, radio frequency power amplifier, low-noise preamplifier, and duplexer. They are integrated into a slim 3D-printed cylinder. The integrated NMR instrument is portable and user-friendly and can reduce the influence of nonideal factors, such as transmission line effects and electromagnetic interference. We conducted different soil moisture experiments with the prototype using Carr–Purcell–Meiboom–Gill pulse sequence to obtain the corresponding transverse relaxation time (T 2) decay curves. Then, the T 2 1D spectrum distributions were obtained by inverse Laplace transformation. Finally, the results reveal that the area of long T 2 component decreases as the soil moisture content decreases.

Mo/4H-SiC Schottky diodes for room temperature X-ray and [formula omitted]-ray spectroscopy

Mo/4H-SiC Schottky diodes were investigated as detectors for their suitability in photon counting X-ray and γ-ray spectroscopy. The Schottky diodes, with a 35μm thick n− epitaxial layer, were treated with a phosphorus pentoxide surface passivation, which had been previously shown to improve the homogeneity of the metal–semiconductor interface and suppress leakage current. One device was coupled to a low-noise charge sensitive preamplifier and standard onwards readout electronics; the resultant spectrometer was used to accumulated X-ray and γ-ray spectra. The spectrometer had an energy resolution of 1.67 keV ± 0.08 keV (97 e− rms ± 5 e− rms) at 5.9 keV and 1.6 keV ± 0.1 keV (93 e− rms ± 6 e− rms) at 59.54 keV. Despite the moderate energy resolution achieved, the results suggested that the leakage current of the Mo/4H-SiC Schottky diode detector was not the dominant source of noise limiting the energy resolution of the spectrometer at the optimum operating conditions at room temperature; lossy dielectrics in close proximity to the input of the preamplifier (including stray dielectrics) and the relatively large average electron–hole pair creation energy of 4H-SiC (an inherent property) were the main contributors to the achieved energy resolution in energy terms.

Optical OFDM Error Floor Estimation by Means of OTDR Enhanced by Front-End Optical Preamplifier.

Optical time-domain reflectometer (OTDR) enables simple identification and localization of a plethora of refractive and reflective events on a fiber link, including splices, connectors and breaks, and measuring insertion/return loss. Specifically, large enough OTDR dynamic range (DR) and thus high signal-to-noise-ratio (SNR) enable clear far-end visibility of longer fibers. We point out here that, under such conditions, the optical bit-error-rate (BER) floor is dominantly determined by reflective events that introduce significant return loss. This complements the OTDR legacy tests by appropriate optical BER floor estimation in the field. As high SNR implies inter-symbol interference as dominating error generating mechanism, we could apply the classical time-dispersion channel model for the optical BER floor determined by the root-mean-square (rms) delay spread of the actual fiber channel power-delay profile. However, as the high-SNR condition is not always fulfilled mostly due to insufficient DR, we propose here inserting a low-noise optical preamplifier as the OTDR front-end to reduce noise floor and amplify the backscattered signal. In order to verify the model for the exemplar test situation, we measured BER on the same fiber link to find very good matching between the measured BER floor values and the ones predicted from the OTDR trace.