A New Circuit Topology for the Realization of Very Low-Noise Wide-Bandwidth Transimpedance Amplifier

In this paper, after discussing some important limitations of the most common circuital configuration that is used for the realization of very low-noise transimpedance amplifiers, we propose and analyze a new circuit topology which allows us to obtain significant advantages as far as equivalent input current noise and bandwidth (BW) are concerned. We present a simple circuit implementation of the new transimpedance amplifier, together with the results of its noise characterization. The comparison between these measurements and those obtained on a conventional transimpedance amplifier with the same transimpedance gain has confirmed that the proposed approach allows us to obtain a lower background noise and a larger BW for the same transimpedance gain.     

Evaluating the bandwidth of an if amplifier in a superheterodyne attenuation meter

Conclusions A superheterodyne attenuation meter, the bandwidth of whose IF amplifier is selected to reduce the random error in measuring a given maximum attenuation, provides smaller random and systematic measurement errors than a meter the bandwidth of whose IF amplifier is selected to provide equal random error components due to frequency instability and thermal noise. Errors in measuring low and medium attenuations will also be smaller with the above method of selecting the IF amplifier's bandwidth, i.e., this bandwidth will be optimum.Translated from Izmeritel'naya Tekhnika, No. 5, pp. 29–31, May, 1967.     

A sensitive magnetoresistive power amplifier

A small, sensitive, low noise, high gain power amplifier, using the anisotropic magnetoresistance effect in thin film permalloy, has been designed and its characteristics calculated. The minimum detectable input current is determined by Johnson noise and hence by input resistance and desired bandwidth. An example of theoretical performance is as follows. For an amplifier unit with approximate dimensions of300 times 300 times 2 mum and with input and load resistances of 50 Ω each the calculated noise at room temperature is equivalent to 10^-8A for a bandwidth (BW) of 1MHz or to 10^-7A for a BW of 100 MHz. At the 10^-8A input current level, the calculated power gain issim 600,000corresponding to a current gain of 775. Power gain decreases with input current asI^{-4/3}, reaching unity atI = 2.1 times 10^{-4}A. Hence, for a BW of 1 MHz, at room temperature, the input current operating range for both amplification and signal-to-noise ratio greater than one is fromI=10^{-8}A to2.1 times 10^{-4}A. To achieve high gain, the amplifier is configured so that the magnetization of the permalloy is biased to lie nominally along the hard axis, the sensing current in the permalloy makes an angle of 45° with the nominal magnetization direction, and the input current produces a magnetic field along the easy axis. This microsize, low noise, silicon compatible power amplifier will be useful in digital and FM applications and possibly as an amplifier for crosstie and bubble memories.     

一种降低D类功率放大器开关噪声的设计

传统D类功率放大器因特有的开关噪声对水下电子设备的信号接收、通信控制和信号传输等电信号产生很大的干扰,限制了D类功率放大器在水下电子设备中的广泛应用针对这一现象,首先阐明了Σ-Δ调制的D类功率放大器降低开关噪声的原理,然后对传统调制方式和Σ-Δ调制方式的D类功率放大器进行原理分析,并在Simulink软件中进行仿真对比。仿真结果表明,传统D类功率放大器在开关频率处的开关噪声能量高,Σ-Δ调制的D类功率放大器的开关噪声能量分散在一定的带宽内,并且开关噪声能量峰值低于传统D类功率放大器。     

Basic characteristics of quantum paramagnetic amplifiers

Conclusions It is advisable to consider as basic those characteristics of a maser whose aggregate completely determines the properties of a maser in its practical application (as an amplifying stage in a receiving system), and whose values can be measured directly. Such characteristics include the amplifier frequency range, amplifier gain, bandwidth, noise temperature at the amplifier input, saturation power, gain instability, and decoupling. Another group of characteristics which can be measured directly is of no particular interest, and includes the restoration time and losses of the amplifier.Finally, a third group of characteristics which are of specific interest and can be determined unambiguously, provided the characteristics of the first two groups are known, includes the paramagnetic amplification factor, resonant maser efficiency, and maser sensitivity and dynamic range.     

Low-Frequency Parametric Amplifier for Small Voltage Measurements

This paper analyzes the low-frequency parametric amplifier, which, in opposition to the parametric amplifiers in the high-frequency range, is wide band and can be realized only simultaneously as an upper and lower sideband up-converter. Three derived basic equations give the possibility of drawing equivalent circuits, in order to calculate gain and stability conditions. The influence of detuning on characteristics of amplifiers is analyzed and investigated experimentally. Cascading more stages of parametric amplifiers is meaningless. The best results can be obtained when the second stage is an upper sideband up-converter. LF parametric amplifiers enable us to achieve a low noise (<0.3 ?V for 100-Hz bandwidth), free from flicker noise, a high input resistance and a high common-mode rejection ratio. For this reason, the amplifier can be applied as the measuring preamplifier of brain voltages.     

Feasibility of an airborne TV camera as a size spectrometer for cloud droplets in daylight

Photographs of clouds taken with a camera with a large aperture ratio must have a short depth of focus to resolve small droplets. Hence the sampling volume is small, which limits the number of droplets and gives rise to a large statistical error on the number counted. However, useful signals can be obtained with a small aperture ratio, which allows for a sample volume large enough for counting cloud droplets at aircraft speeds with useful spatial resolution. The signal is sufficient to discriminate against noise from a sunlit cloud as background, provided the bandwidth of the light source and camera are restricted, and against readout noise. Hence, in principle, an instrument to sample the size distribution of cloud droplets from aircraft in daylight can be constructed from a simple TV camera and an array of laser diodes, without any components or screens external to the aircraft window.     

Low noise patch‐clamp current amplification by nanoparticles plasmonic–photonic coupling (analysis and modelling)

In this article, a patch‐clamp low noise current amplification based on nanoparticles plasmonic radiation is analyzed. It is well‐known, a very small current is flowing from different membrane channels and so, for extra processing the current amplification is necessary. It is notable that there are some problems in traditional electronic amplifier due to its noise and bandwidth problem. Because of the important role of the patch‐clamp current in cancer research and especially its small amplitude, it is vital to intensify it without adding any noises. In this study, the current amplification is performed firstly: from the excitement of nanoparticles by the patch‐clamp pico‐ampere current and then, the effect of nanoparticles plasmonic far‐field radiation on conductor''s carriers, which will cause the current amplification. This relates to the plasmonic‐photonic coupling and their effect on conductor carriers as the current perturbation agent. In the steady state, the current amplification can reach to 1000 times of initial level. Furthermore, we investigated the nanoparticles morphology changing effect such as size, nanoparticles inter‐distance, and nanoparticles distance from the conductor on the amplifier parameters. Finally, it should note that the original aim is to use nanoparticles plasmonic engineering and their coupling to photonics for output current manipulating.Inspec keywords: nanoparticles, plasmonics, biomembranes, low noise amplifiers, cancer, bioelectric phenomena, nanomedicine, biomedical electronicsOther keywords: output current manipulation, NP plasmonic engineering, amplifier parameters, NP morphology changing effect, steady state, current perturbation agent, conductor carrier effect, NP plasmonic far‐field radiation effect, patch‐clamp picoampere current, bandwidth problem, noise, traditional electronic amplifier, membrane channels, nanoparticle plasmonic radiation, nanoparticle plasmonic‐photonic coupling analysis, low noise patch‐clamp current amplification     

A 100 A, 100 kHz transconductance amplifier

A high-current, wide-band transconductance amplifier is described that provides an unprecedented level of output current at high frequencies with exceptional stability. It is capable of converting a signal voltage applied to its input into a ground-referenced output rms current up to 100 A over a frequency range from DC to 100 kHz with a useable frequency extending to 1 MHz. The amplifier has a 1000-W output capability ±10 V of compliance, and can deliver up to 400 A of pulsed peak-to-peak current. The amplifier design is based on the principle of paralleling a number of precision bipolar voltage-to-current converters. The design incorporates a unique ranging system controlled by opto-isolated switches, which permit a full-scale range from 5 A to 100 A. The design considerations for maintaining wide bandwidth, high output impedance, and unconditional stability for all loads are discussed     

Broad-Band Remote-Sensing Magnetometer

A broad-band remote-sensing magnetometer system has been developed for measuring fast-rising pulsed magnetic fields. Broad frequency response is achieved by frequency modulating a 1.5-GHz microwave carrier for transmission from the sensor to a remotely located receiver. The primary field probe is a ferrite-loaded coil, which produces a current proportional to the magnetic-field intensity. This current is used to frequency modulate a YIG-tuned transistor oscillator in the sensor. A traveling-wave amplifier in the receiver provides carrier amplification and amplitude limiting because it is operated in saturation mode. A new type of FM discriminator, which offers multiple-octave bandwidth potential, converts the frequency-modulated carrier to an amplitude-modulated carrier. The signal is finally detected and amplified for oscilloscope display. While the present system achieves a 50-MHz bandwidth, the system concept should be capable of extension to several times this bandwidth.     

Spatiotemporal heterodyne detection

We describe a scheme in which a camera is turned into an efficient tunable frequency filter of a few-Hertz bandwidth in an off-axis, heterodyne optical mixing configuration, enabling one to perform parallel, high-resolution coherent spectral imaging. This approach is made possible through the combination of a spatial and temporal modulation of the signal to reject noise contributions. Experimental data obtained with dynamically scattered light by a suspension of particles in Brownian motion is interpreted.     

基于光子计数调制的光学时域反射测量

针对光学时域反射测量的信噪比受到光子计数的量子起伏的影响,本文提出了光子计数调制技术应用于1.55μm单光子探测光时域反射测量系统,该方法根据相干光场量子涨落的噪声功率在频域上具有均匀分布的特性,采用光子计数调制与锁相放大器解调的方法抑制了量子起伏.实验结果表明,通过改变锁相放大器的积分时间设置滤波带宽,改善了光子计数的信噪比.与光子计数直接测量的结果相比,光子计数调制的光学时域反射测量的信噪改善比达到28.3 dB.     

How to enlarge the bandwidth without increasing the noise in OP-AMP-based transimpedance amplifier

Increasing the bandwidth without degrading the noise performance represents the main challenge in the design of transimpedance amplifiers. This paper presents a novel circuit topology for a transimpedance amplifier that allows obtaining an improved tradeoff between equivalent input noise and bandwidth with respect to the conventional approach. The effectiveness of the new topology has been demonstrated by designing and testing a prototype of a transimpedance amplifier based on the proposed topology.     

Random Errors in Time Interval Measurement Based on SAW Filter Excitation

This paper deals with the time interval measurement method that makes use of a surface acoustic wave (SAW) filter as a time interpolator. The method is based on the fact that a transversal SAW filter excited by a short pulse can generate a finite signal with highly suppressed spectra outside a narrow frequency band. If the responses to two excitations are sampled at clock ticks, they can be precisely reconstructed from a finite number of samples and then compared to determine the time interval between the two excitations. We have analyzed noise contributions to the overall uncertainty of the interval measurement. The following four noise sources have been considered: (1) noise of excitation; (2) noise of amplifier; (3) quantization noise of the analog-to-digital converter; and (4) clock and sampling jitter. The main goal of the analysis was to determine the uncertainty of the measurement in dependence on the variances of contributing noises, and the magnitude of the frequency response of the filter. First, each uncertainty component has been analyzed under general assumptions. Second, a general narrow-band filter has been investigated. Finally, we have found the solution for an ideal narrow-band filter where we have obtained simple illustrative results. The results have been compared to Monte-Carlo simulations. Good agreement between theory and simulation has been demonstrated except for the outliers due to the false ambiguity solution that occurs with large measurement errors and small relative filter bandwidth.     

Frequency translation of light waves by propagation around an optical ring circuit containing a frequency shifter: II. Theoretical analysis

Theoretical aspects of the frequency-translation ring circuit are considered through numerical simulations. We analyze the signal and noise propagation around an optical ring circuit that contains a frequency shifter, an erbium-doped fiber amplifier and a bandpass filter (BPF). The relations between the frequency-translation limit and some important parameters such as the BPF bandwidth and the polarization state are clarified. Numerical results for the frequency-translation limit are compared with reported experiments and a frequency translation of more than 100 GHz is predicted.     

基于麦克风阵列的变速器噪声源定位研究

对一款轿车变速器存在的噪声问题进行研究。分析变速器噪声的组成部分。对该变速器进行半消声室台架实验,通过频谱分析、贡献量分析等方法找到特征频率。计算发现该问题较为特殊,针对因设计不当出现不同传动部件特征频率一致的情况,利用声学照相机技术基本确定辐射声源位置。考虑噪声特征频率范围与箱体的模态频率范围较为接近,通过有限元法计算箱体的模态频率,发现箱体出现共振。研究为修改传动部件参数、变速器箱体结构提供参考依据。     

CMOS chopper amplifier for chemical sensor

A highly sensitive CMOS chopper amplifier for an oxygen probe is described. It is integrated in a 2-μm double-poly p-well CMOS process. The chip uses only a single 5-V voltage source, and no external components are needed. It is realized by using the current mode chopper technique to overcome the low frequency noise and drift problems. The clock feedthrough generated by the chopper circuit is reduced by using the switched-capacitor-filter technique. The switched-capacitor technique is also used to implement the function of demodulation. The simulated current is converted into an output voltage with a slope of approximately 100 mV/nA. The current signal from 0.2 to 8 nA can be measured with a nonlinearity of 3.5%. Experimental results are given showing the performance of this amplifier     

Front-end receiver electronics for high-frequency monolithic CMUT-on-CMOS imaging arrays

This paper describes the design of CMOS receiver electronics for monolithic integration with capacitive micromachined ultrasonic transducer (CMUT) arrays for highfrequency intravascular ultrasound imaging. A custom 8-inch (20-cm) wafer is fabricated in a 0.35-μm two-poly, four-metal CMOS process and then CMUT arrays are built on top of the application specific integrated circuits (ASICs) on the wafer. We discuss advantages of the single-chip CMUT-on-CMOS approach in terms of receive sensitivity and SNR. Low-noise and high-gain design of a transimpedance amplifier (TIA) optimized for a forward-looking volumetric-imaging CMUT array element is discussed as a challenging design example. Amplifier gain, bandwidth, dynamic range, and power consumption trade-offs are discussed in detail. With minimized parasitics provided by the CMUT-on-CMOS approach, the optimized TIA design achieves a 90 fA/√Hz input-referred current noise, which is less than the thermal-mechanical noise of the CMUT element. We show successful system operation with a pulseecho measurement. Transducer-noise-dominated detection in immersion is also demonstrated through output noise spectrum measurement of the integrated system at different CMUT bias voltages. A noise figure of 1.8 dB is obtained in the designed CMUT bandwidth of 10 to 20 MHz.     

Origin of 1/f PM and AM noise in bipolar junction transistor amplifiers

In this paper we report the results of extensive research on phase modulation (PM) and amplitude modulation (AM) noise in linear bipolar junction transistor (BJT) amplifiers. BJT amplifiers exhibit 1/f PM and AM noise about a carrier signal that is much larger than the amplifiers thermal noise at those frequencies in the absence of the carrier signal. Our work shows that the 1/f PM noise of a BJT based amplifier is accompanied by 1/f AM noise which can be higher, lower, or nearly equal, depending on the circuit implementation. The 1/f AM and PM noise in BJTs is primarily the result of 1/f fluctuations in transistor current, transistor capacitance, circuit supply voltages, circuit impedances, and circuit configuration. We discuss the theory and present experimental data in reference to common emitter amplifiers, but the analysis can be applied to other configurations as well. This study provides the functional dependence of 1/f AM and PM noise on transistor parameters, circuit parameters, and signal frequency, thereby laying the groundwork for a comprehensive theory of 1/f AM and PM noise in BJT amplifiers. We show that in many cases the 1/f PM and AM noise can be reduced below the thermal noise of the amplifier.     

Ultra low-noise preamplifier for low-frequency noise measurementsin electron devices

The design and realization of an ultra-low-noise, high-input-impedance amplifier for low-frequency noise measurements in electronic devices is presented. Special care is devoted to the solution of typical problems encountered in the design of low-noise low-frequency equipment, such as power supply noise and temperature fluctuations. The ultra-low-noise preamplifier has a bandwidth of over seven decades with a low-frequency roll-off of 4 mHz. The noise characteristics obtained are sensibly better than those of commercial preamplifiers commonly adopted in low-frequency noise measurements. The application of this preamplifier to the realization of standard 1/f^γ noise generators is presented