Low-noise Preamplifier Research Articles

Shot noise measurement methods in electronic devices

The limitations to shot noise measurement methods based on superconducting quantum interference device (SQUID) and superconductivity-insulation-superconductor (SIS) Josephson junction are pointed out, and a method to measure the shot noises of conventional electronic devices is proposed. Shot noise characteristics of conventional electronic devices are analyzed, and then a low-temperature measurement system is established. By using a double-shielding construction and low noise preamplifier, the test system can achieve a good electromagnetic interference shielding and low background noise. The theoretical and the experimental results of shot noises in diodes at 10 K are in good agreement with each other. The accuracy and the credibility of measurement system are proved.

Ultra-low-noise preamplifier for condenser microphones

The paper presents the design of a low-noise preamplifier dedicated for condenser measurement microphones used in high sensitivity applications, in which amplifier noise is the main factor limiting sensitivity of the measurements. In measurement microphone preamplifiers, the dominant source of noise at lower frequencies is the bias resistance of the input stage. In the presented solution, resistors were connected to the input stage by means of switches. The switches are opened during measurements, which disconnects the resistors from the input stage and results in noise reduction. Closing the switches allows for fast charging of the microphone capacitance. At low frequencies the noise of the designed preamplifier is a few times lower in comparison to similar, commercially available instruments.

The MEMSamp: using (RF-)MEMS switches for the micromechanical amplification of electronic signals

Semiconductor-based electronic amplifiers are ubiquitous in the modern world, but have fundamental limitations, such as the impossibility of using them at extreme temperatures and their sensitivity to ionizing radiation. Also, they inherently have various sources of electronic noise. We have developed a MEMS (micro-electromechanical systems) switch based amplifier in which an electronic signal is mechanically amplified in power: the MEMSamp. The new device is suitable for the same applications as semiconductor-based amplifiers, with the additional advantage of a purely mechanical operation, circumventing the limitations mentioned above. A thermal noise analysis shows that a MEMSamp may be operated with much lower input noise than state-of-the-art semiconductor amplifiers. We expect optimized amplifiers based on this principle to be applicable in fields ranging from low-noise preamplifiers to radiation-hard power amplifiers, and from ultra-high temperature electronics to spacecrafts.

A LOW-NOISE LOW-POWER FRONT-END AMPLIFIER FOR NEURAL-RECORDING APPLICATIONS

Monitoring the electrical activities of a large number of neurons in vertebrates' central nervous system in vivo through hundreds of parallel channels without interferring in their natural functions is a neuroscientist's interest. Value of this information in both scientific and clinical contexts, especially in expansion of brain–computer interfaces, is extremely significant. Therefore, low-noise amplifiers are needed with filtering capability on the front end to amplify the desired signals and eliminate direct current baseline shifts. Hence, size and power consumption need to be minimized to reduce trauma and heat dissipation, which can result in tissue damage for human applications and the system needs to be implantable and wireless. The practical solution for developing such systems is system-on-a-chip, based on ultra-low-power mixed-mode and wideband RFIC designs. They, however, impose a number of challenges that may require nontraditional solutions. In this paper, we present a fully differential low-power low-noise preamplifier suitable for recording biological signals, from a few mHz up to 10 kHz. This amplifier has a bandpass filter that is tunable between 10 mHz and 10 kHz, and has been designed and simulated in a standard 90-nm CMOS process. The circuit consumes 10 μW from a 1.2 V supply and provides a gain of 40 dB and an output swing of ±0.5 V with a total harmonic distortion of less than 0.5%. The total input-referred noise level is 4.6 μV integrating the noise over 0.01 Hz to 10 kHz.

Analytical Model for Obtaining the Ionization Rate Ratio of Mesa InAlAs Avalanche Photodiodes

We proposed a new analytical model to extract the effective ionization rate ratio k from the measured multiplication noise of Avalanche photodiodes (APDs). In this model, k was expressed as a function of the multiplication factor M. We extracted the effective k of the mesa-structured InAlAs APDs using this model. A measurement system that consisted of a low-noise differential preamplifier was developed for this purpose, leading to the measurements of the noise data, particularly in the region where it was small. APD noise data could be fitted to the curve based on this new analytical model better than with other analytical models over the wide range of M. The effective k in the region where M was small became appropriate using this model. The quantum efficiency of the APDs was also found to be reasonable compared with the results obtained using the other analytical models.

Cryogenic Performance of a Low-Noise JFET-CMOS Preamplifier for HPGe Detectors

Cryogenic low-noise charge sensitive preamplifiers have been developed and realized for the GERmanium Detector Array (GERDA). An integrated JFET-CMOS preamplifier, which is fully functional at cryogenic temperatures, has been tested in conjunction with an unsegmented p-type HPGe detector. Both the crystal and the preamplifier were operated inside a liquid nitrogen dewar at 77 K. The detector capacitance was ~60 pF. An optimum resolution of 1.6 keV FWHM has been obtained for the pulser line at 6 ¿s shaping time. A resolution of 2.1 keV FWHM has been achieved for the 1.332 MeV line from a <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">60</sup> Co source. A wide bandwidth (rise time of ~16 ns) permits use of pulse-shape analysis techniques to localize the position of the photon interactions inside the crystal. A low power consumption (~23 mW) makes the preamplifier suitable for a multi-channel array of germanium detectors.

Automatic Offset Cancellation and Time-Constant Reduction in Charge-Sensitive Preamplifiers

A circuit technique is presented which eliminates the offset at the output of charge-sensitive preamplifiers and optionally reduces the resistive reset time-constant. Offset cancellation as well as time-constant reduction are obtained with no trimming. Offset cancellation is obtained actively through a negative feedback path whose ?error? variable is the offset itself. As a result the output voltage offset is automatically eliminated, irrespective of the bias point of the input transistor and the dark current of the sensor connected to the preamplifier. Using the proposed technique in low-noise charge preamplifiers for germanium detectors typical offsets in the range 100-300 mV are reduced to ±2 mV. The noise of the preamplifier is unaffected by the offset cancellation circuit. Moreover, by insertion of an optional resistor in the proposed circuitry the decay time-constant of the preamplifier is automatically reduced by a factor of up to 10, while leaving unchanged the noise and the sensitivity of the charge preamplifier. This improves pulse separation at the preamplifier's output, which can be particularly useful for pattern recognition at high event rates. The realized offset-free circuit features an equivalent noise of 650 eV fwhm in germanium at 3 ?s shaping time, i.e. an Equivalent Noise Charge of ~ 94 electrons r.m.s. and a dynamic range in excess of 86 dB, which makes it perfectly suited for high-resolution gamma-ray spectrometry with large germanium detectors.

Analysis and Design of a Multistage CMOS Band-Pass Low-Noise Preamplifier for Ultrawideband RF Receiver

A CMOS low-noise preamplifier for application in a 3.1-10.6-GHz ultrawideband radio-frequency (RF) receiver system is presented. This is essentially a wideband-pass multistage RF preamplifier using a cascade of a three-segment band-pass LC ? -section filter with a common-gate stage as the front end. Fundamental design analysis in terms of gain, bandwidth, noise, and impedance matching for the amplifier is presented in detail. The preamplifier was fabricated using the low-cost TSMC 0.18-?m 6M1P CMOS process technology. The amplifier delivered a buffered power gain (S 21) of ? 14 dB with a -3-dB bandwidth (between the corner frequencies) of around 7.5 GHz. It consumed around 30 mW from a 2.5-V supply voltage. It had a minimum passband noise figure of around 4.7 dB, an input-referred third-order intercept point of -5.3 dBm, and reverse isolation (S 12) under -65 dB.

A pulse nuclear quadrupole resonance spectrometer

A pulse nuclear quadrupole resonance (NQR) spectrometer intended for studying the resonance signal spectra of nuclei of solid substances in a 1- to 30-MHz band is described. The pulse duration of excitation pulses is regulated from 10 to 100 μs at a 5- to 100-Hz pulse repetition rate. The spectrometer ensures a probing pulse power of up to 1.5 kW and is characterized by the availability of an NQR signal simulator, a low-noise preamplifier, and a phase detector with a dynamic range exceeding 100 dB. The efficiency of the spectrometer has been tested by studying the NQR spectrum of 14N nuclei in urotropine. The spectrometer ensured a possibility of detecting 0.2 g of urotropine.

Cryogenic receive coil and low noise preamplifier for MRI at 0.01 T

We have investigated the design and construction of liquid nitrogen cooled surface coils made from stranded (litz) copper wire for low field MRI applications. If designed correctly, cooled litz coils can provide a competitive alternative to high temperature superconducting (HTS) coils without the complications associated with flux trapping. Litz coils can also be produced with a wider range of shapes and sizes, and at lower cost. Existing models were verified experimentally for flat spiral coils wound from solid and litz wires, operated at room temperature and 77 K, and then used to design and optimise a cooled receive coil for MRI at 0.01 T (425 kHz). The Q-factor reached 1022 when the coil was cooled to 77 K, giving a bandwidth of just 0.42 kHz, so a low noise JFET preamplifier was developed to provide active damping of the coil resonance and thus minimise image intensity artefacts. The noise contribution of the preamplifier was determined using a method based on resistive sources and image noise analysis. The voltage and current noise were measured to be 1.25 nV/ Hz 1/2 and 51 fA/ Hz 1/2, respectively, and these values were used to estimate a noise figure of 0.32 dB at the resonant frequency of the cooled coil. The coil was used to acquire 0.01 T spin echo images, first at room temperature and then cooled to 77 K in a low noise liquid nitrogen cryostat. The measured SNR improvement on cooling, by a factor of 3.0, was found to correspond well with theoretical predictions.

Soil moisture assessment by means of compressional and shear wave velocities: Theoretical analysis and experimental setup

In previous works, the authors presented the outline of a method for measuring the moisture content in agricultural soils via elastic waves, along with experimental results obtained on a specimen of sandy soil. This work illustrates other aspects and results of the research, regarding both the underlying theory and the design and realization of an improved measurement system. Firstly, the derivation of the simplified equations which are at the basis of the moisture measurement is thoroughly illustrated and discussed, starting from the more complex (and generally unmanageable) equations of elastic waves in unconsolidated porous media. The analysis suggests that by measuring the velocities of low-frequency compressional and shear waves in soils, it is possible not only to measure the water content, but also the uniformity in the water distribution. Secondly, the design and the practical realization of an experimental setup, which is able to measure the velocity of compressional and shear waves in soils, is illustrated in detail. The use of custom-built compressional and shear waves electromechanical actuators, together with geophones, low noise preamplifiers, and suitable signal processing techniques, brought to the realization of an effective and reasonably accurate measurement system.

Low-noise low-power CMOS preamplifier for multisite extracellular neuronal recordings

This paper reports the design and the experimental results of a fully integrated, low-noise, low-power standard CMOS preamplifier circuit used to record the extracellular electrophysiological activity of in vitro biological neuronal cultures. Our goal is to use the preamplifier in a fully integrated, multi-channel, bi-directional neuro-electronic interface.Among others, two main requirements must be addressed when designing such kind of integrated recording systems: noise performance and very low frequency disturbance rejection. These two requirements need to be satisfied together with a small silicon area design, to be able to integrate a large number of recording channels (i.e. up to thousands) onto a single die. A prototype preamplifier circuit has been designed and implemented; in this paper we report the experimental results.While satisfying the above requirements, our circuit offers state-of-the-art smallest area occupation (0.13mm2) and consumes 4.5μW. Sub-threshold-biased lateral pnp transistors, used to implement very high resistance value integrated resistors, have been characterized to determine the resistance spread.The fabricated prototype, coupled with a commercial Micro-Electrode Array (MEA), has been successfully employed to record the extracellular electrophysiological spontaneous activity, both of muscular cardiac cells (cardiomyocytes) and of spinal cord neurons from murines.

An ultralow noise preamplifier for low frequency noise measurements

Low frequency noise measurements are among the most sensitive tools for the investigation of the quality and of the reliability of semiconductor devices. The sensitivity that can be obtained depends on the background noise of the low noise preamplifier coupled to the device under test (DUT) that, at very low frequencies, is dominated by flicker noise. The low frequency noise produced by the DUT, on the other end, is very often the most interesting signal to be detected and analyzed. In this work we propose a very simple topology for the realization of a general purpose low noise preamplifier whose noise performances, at very low frequencies (below 10 Hz), are significantly better than those that can be obtained by the most popular commercial instrumentation. Indeed, a gain of 80 dB with a pass band extending from a few tens of mHz up to a few kHz with an equivalent input voltage noise as low as 14 nV/square root(Hz) (100 mHz), 1.4 nV/square root(Hz) (1 Hz), 1.0 nV/square root(Hz) (10 Hz), and 0.8 nV/square root(Hz) (1 kHz) are consistently obtained by using quite standard electronic components and with no need for trimming and/or calibration steps. Moreover, the junction field-effect transistor input stage of the amplifier is characterized by an equivalent input current noise below 4 fA/square root(Hz) in the entire bandwidth, resulting in negligible background noise degradation for DUT impedances in excess of 100 kohms.

Novel Design of Low Noise Preamplifier for Medical Ultrasound Transducers

A novel design of low noise amplifier for medical ultrasound transducers is described in this paper. Unlike conventional low noise preamplifiers, this design proposes a new circuit configuration which has electronically adjustable matching resistance that allows the preamplifier to be compatible with a variety of medical ultrasound transducers. The design employs current feedback operational amplifier to enhance the gain-bandwidth independence and improve the design slew rate. Simulation results show that the proposed design has very low output noise voltage spectral density and the level of this noise does not increase when its tunable matching resistance is increased or decreased.

Portable gamma-ray tracking system for nuclear material safety

Using a CsI (Tl)-coupled PIN-type photodiode of 1 cm×1 cm and compact data acquisition system, a portable gamma monitoring system with lower cost has been fabricated and tested for gamma detection. After evaluating spectroscopy performance for gamma emission radioisotopes of Co-57 and Cs-137, we integrated the DAS with low-noise preamplifier, shaping amplifier, discriminator and multi-control unit (MCU) to acquire cumulative gamma detection data. The data are continuously sent to an observer, through a wireless telecommunication module of 400 MHz band, to monitor whether any gamma emitting material is out of sight or any accident takes place. A comparative study of gamma spectroscopy between our detector and a commercialized detector has been performed.

Development of scanning field emission current microscopy

Spatial uniformity and durability of field emission are main issues in carbon nanotube (CNT) field emission devices fabricated by a screen-printing process. In this paper, we propose a novel method to visualize field emission sites of CNT films two-dimensionally by adopting scanning probe microscopy. While an anode probe with a small tip diameter of <100 nm was scanned over a CNT emitter surface whose dimension is 200 μm × 200 μm, the field emission current was recorded by a Keithley 6517A, SR570 (low-noise current preamplifier) and NI USB-6009 (data acquisition board), converted into 256 grayscale level, and displayed on a monitor through the LabView™ program. The anode probe was made by electrochemically etching tungsten wire and the CNT emitter sample was fabricated by screen-printing multiwall CNTs whose diameter is 4–6 nm and length 1–2 μm on indium-tin-oxide (ITO) glass. During scanning, the gap between W anode and ITO glass surface was maintained to be a few tens of μm. For large-scale imaging, we used an inertial nano-positioner whose model number is ANPxyz100, made by Attocube Systems, as a long-range scanner. With this system, we could obtain an electron emission current map over large surface areas under constant anode voltage.

Influence of noise parameters of integral operational amplifiers and voltage comparators and their nonlinear distortions on presentation accuracy of signals being processed

Influence of noisy signals of integral operational amplifiers (IOAs) and voltage comparators (IVCs) on accurate parameters of low-noise preamplifiers, discriminators, and analog-to-digital converters (ADCs) is considered. Methods aimed at increasing the noise factor of the above devices are discussed. Influence of nonlinear distortions resulting from signal representation is taken into consideration

Fabrication and performance characteristics of a CsI(Tl)/PIN diode radiation sensor for industrial applications

CsI(Tl)/PIN diode radiation sensors were fabricated for application in various fields such as an NDT and an environmental radiation monitoring system. CsI(Tl) crystals of 11×11×21 mm 3 were processed as optical grade from a CsI(Tl) ingot and matched with PIN diodes in consideration of the light loss and the external impact. The photodiode signal is amplified by a low-noise preamplifier and a pulse shape amplifier. At room temperature, the fabricated CsI(Tl)/PIN diode radiation sensors demonstrate an energy resolution of 7.9% for 660 keV gamma rays and 4.9% for 1330 keV. The fluctuation of the directional dependency was below 14% from 0 to 90 degree for the incident 660 keV gamma rays. The compactness, the low-voltage power supply and the physical hardness are very useful features for industrial applications of the fabricated CsI(Tl)/PIN diode sensor.

Annular gas ionization detector for low energy heavy ion backscattering spectrometry

A gas ionization chamber for use in backscattering spectrometry has been built. It has the shape of a hollow cylinder and can be placed in-line with the incident ion beam. The entrance window for detected particles is composed of a circular array of silicon nitride membranes. A low noise preamplifier with cooled FET is used for charge amplification. The detector resolution has been measured for a variety of ions in the mass range from He to Si and for energies between 0.5 and 8 MeV. The energy resolution of the ionization chamber surpasses the one of a state-of-the-art silicon charged particle detector for all ions heavier than Li. For Si ions the improvement in resolution is more than a factor of 2. The device does not suffer from any radiation damage. For He particles around 1 MeV the resolution is between 13 and 16 keV (FWHM). Therefore the new detector is not only well suited for heavy ion backscattering spectrometry but can also be applied for standard He RBS, allowing the use of a single detector for all types of projectiles in a wide energy range.

Single-photon counting at 950–1300 nm: using InGaAsP photocathode–GaAs avalanche diode hybrid photomultiplier tubes

We describe the single-photon counting performance of a hybrid photomultiplier tube (HPMT) near-infrared (950–1300 nm) detector with a transfered electron InGaAsP photocathode and a GaAs Schottky avalanche diode anode. These devices have a lower photoelectron multiplication gain than conventional photomultiplier tubes, but offer a greater linear dynamic range and electrical bandwidth. With the use of a low-noise preamplifier, they can detect single photons with a greater than 20% quantum efficiency (QE) and a reasonably low dark-noise count rate. The avalanche diode at the anode operates in a low gain analog mode and has no afterpulsing. As a result, these HPMTs can detect single photons continuously at high count rates without gating. The relatively large photocathode active area (1 mm diameter) is also attractive to many applications including laser altimetry, ranging, and free-space communications through the atmosphere. We measured 25% photocathode QE and nearly the same single-photon detection efficiency at 1064 nm wavelength with a dark count rate of 60,000 per second at −22°C. The output pulse width in response to single-photon detection is about 0.8 ns. The maximum count rate exceeded 100 million counts per second and was limited only by the speed of the electronics. The rms timing jitter of the HPMT output was measured to be about 0.5 ns. The jitter is dominated by the electron diffusion time within the photocathode and can be improved by reducing the photocathode thickness at a small loss in photocathode QE. We evaluated several of these HPMTs and detailed measurement results are reported in this paper.