仪表放大器AD623的性能与应用

介绍单片仪表放大器AD623的结构原理和主要特性参数，给出了应用实例，并对应用中的问题做了说明。     

Coal mine roof rating(CMRR), rock mass rating(RMR) and strata control:Carborough Downs Mine,Bowen Basin,Australia

The rock mass rating(RMR) has been used across the geotechnical industry for half a century. In contrast,the coal mine roof rating(CMRR) was specifically introduced to underground coal mines two decades ago to link geological characterization with geotechnical risk mitigation. The premise of CMRR is that strength properties of mine roof rock are influenced by defects typical of coal measures stratigraphy.The CMRR has been used in longwall pillar design, roof support methods, and evaluation of extended cuts,but is rarely evaluated. Here, the RMR and CMRR are applied to a longwall coal mine. Roof rock mass classifications were undertaken at 67 locations across the mine. Both classifications showed marked spatial variability in terms of roof conditions. Normal and reverse faulting occur across the mine, and while no clear relationships exist between rock mass character and faulting, a central graben zone showed heterogeneous rock mass properties, and divergence between CMRR and RMR. Overall, the CMRR data fell within the broad envelope of results reported for extended cuts at Australian and U.S. coal mines. The corollary is that the CMRR is useful, and should not be used in isolation, but rather as a component of a strata control programme.     

一种用于角度传感器中的仪表放大器

主要设计了一种用于角度传感器系统中的仪表放大器。为了满足角度传感器系统中对信号频率的要求,需要仪表放大器的带宽足够宽能够达到3.3 MHz。该电路采用标准三运算放大器结构电路,以折叠共源共栅结构的放大器为基础,对共模信号进行抑制,对差分信号进行放大,提高了放大器的精度,增大了仪表放大器的带宽。采用Chartered 0.35μm CMOS双栅工艺对电路进行仿真和流片验证,测试结果表明:在0.8～2.85 V内,仪表放大器的共模抑制比达到了102 dB,带宽能够达到3.3 MHz,输出摆幅为1.7 V,电路功能良好,达到了设计要求,该电路可用于汽车电子以及医疗设备系统。     

电荷泵型LED驱动器的CMOS误差放大器设计

结合电荷泵型LED驱动器的工作要求,从减小输出电压纹波、稳定输出电压出发,设计了一款误差放大器。该误差放大器具有较大的工作电压范围,使电荷泵型LED驱动器高效率低噪声工作。基于CHRT0．35μm CMOS MIXED SIGNAL TECHNOLOGY进行仿真,结果表明,在2．7～5V工作电压范围内,开环电压增益约等于72dB,相位裕度约等于65°,单位增益带宽约等于4．6MHz,共模抑制比CMRR约等于113dB,电源抑制比PSRR约等于100dB。     

有效值法交流共模抑制比测量不确定度评定

为解决影响工业现场的数据采集系统精度的共模干扰问题,以波形分析方式研究了交流共模干扰的表现形式,揭示了其同时含有直流偏移叠加交流波动和本底噪声的典型特征。提出以波形有效值幅度进行干扰强度表征,并进行共模抑制比的定量表述;同时使用有效值叠加模型对系统本底噪声的影响予以剔除,提高了共模抑制比的测量精度。基于该方法与流程讨论了其主要的不确定度来源—信号源误差、数据采集系统增益误差、幅度测量误差、幅度分辨力误差以及测量重复性等。进行了测量不确定度分析和评价,结合实例给出了通道共模抑制比的不确定度评价结果,验证了所述方法的实用性与可行性。     

Theoretical study of the circuit architecture of the basic CFOA and testing techniques

This paper examines the closed-loop characteristics of the basic Current-Feedback Operational Amplifier (CFOA), and in particular, the dynamic response. Additionally, it also examines the design and advantages of the CFOA regarding its ability to provide a significantly constant closed-loop bandwidth for closed-loop voltage gain. Secondly, the almost limitless slew–rate provided by the class AB input stage that makes it superior to the voltage-mode operational amplifier (VOA) counterpart. Additionally, this paper also concerns the definitions and measurements of the terminal parameters of the CFOA, regarded as a ‘black box’. It does not deal with the way that these parameters are related to the properties of the active passive and active components of a particular circuit configuration. Simulation is used in terminal parameter determination: this brings with it the facility of using test conditions that would not normally prevail in a laboratory test on silicon implementations of the CFOAs. Thus, we can apply 1mA and 1mV test signals from, respectively, infinite and zero source impedances that range in frequency from d.c to some tens of GHz. Also, we assume the existence of resistors with identical Ohmic value and very high value ideal capacitors. Where appropriate, practical test methods are referred to physical laboratory prototypes.     

Ultra low voltage, high performance operational transconductance amplifier and its application in a tunable Gm-C filter

This paper presents an ultra low voltage, high performance Operational Transconductance Amplifier (OTA) and its application to implement a tunable Gm-C filter. The proposed OTA uses a 0.5 V single supply and consumes 60 μw. Employing special CMFF and CMFB circuits has improved CMRR to 138 dB in DC. Using bulk driven input stage results in higher linearity such that by applying a 500 mv_p-p sine wave input signal at 2 MHz frequency in unity gain closed loop configuration, third harmonic distortion for output voltage is −46 dB and becomes −42.4 dB in open loop state for 820 mv_p-p output voltage at 2 MHz. DC gain of the OTA is 47 dB and its unity gain bandwidth is 17.8 MHz with 20 pF capacitance load due to both deliberately optimized design and special frequency compensation technique. The OTA has been used to realize a wide tunable Gm-C low-pass filter whose cutoff frequency is tunable from 1.4 to 6 MHz. Proposed OTA and filter have been simulated in 0.18 μm TSMC CMOS technology with Hspice. Monte Carlo and temperature dependent simulation results are included to forecast the mismatch and temperature effects after fabrication process.     

Cascadable current mode instrumentation amplifier

In this paper, a Current Mode Instrumentation Amplifier (CMIA) is presented. The proposed circuit employs two Extra X Current Controlled Current Conveyors (EX-CCCII) and a single grounded resistor. The circuit offers a wide differential-gain bandwidth, wide CMRR bandwidth, and electronically tunable differential gain. The circuit offers cascadibility feature with input impedance of 2.167 kΩ which is very small in comparison to the output impedance of 2.17 MΩ. Simultaneously, a Transresistance (TR) instrumentation amplifier is also obtained with the features of electronically tunable high differential gain and wide bandwidth. The effect of non-idealities of EX-CCCII on the circuit performance is also analysed. The validity of the proposed circuit is verified through PSPICE simulations using 0.25 µm parameters with a supply voltage of ±1.25 V. Also, the circuit is verified by experimental results.     

基于非理想运放模型的共模抑制比的研究

研究分析了典型放大器共模抑制比的计算模型,根据影响共模抑制比的因素和一般计算模型的缺点,在基于非理想运放的基础上,提出一种共模抑制比的计算模型。经验证,提出的计算模型和方法能够改善高共模抑制比,并且是有效合理的。     

噪声温度计用放大器设计与性能评估

低噪声、低失真、高共模抑制比的放大器对于噪声法测量热力学温度至关重要。设计了由前置放大、仪表放大和缓冲放大3级组成的噪声温度计用高性能放大器。其中,采用具有超低噪声的结型场效应对管IF9030作为前置差分放大级的输入;研制了自动化测量对管转移特性的装置,用于在大批量对管中挑选匹配度更优的器件;采用互相关技术压低电路中不相关的噪声,从而确保能够准确测量到被放大器背景噪声淹没的非线性失真信号;重点评估了放大器在1MHz带宽内的共模抑制比和放大器受双频激励时的非线性失真。测量结果表明,放大器的背景噪声为1.2nV/Hz1/2;100kHz带宽内的共模抑制比优于90dB,100kHz至1MHz带宽内的共模抑制比会随着频率的增加而降低,但不低于70dB;放大器受频率为400kHz、401kHz,幅度有效值为8μV的双频信号激励时,产生的二阶交调失真信号比双频信号低79dB,二阶谐波失真信号比双频信号低85dB。