共查询到20条相似文献，搜索用时 400 毫秒
1.
宋荣 《深圳职业技术学院学报》2009,(3)
介绍一种以运算放大器为核心器件,通过NPN型三极管集电极输出的高压小电流精密恒流源电路,分析了电路的工作原理、重要元件的参数选择及电压检测电路带来的电流误差,给出了以运算放大器比例运算电路实现补偿的方法.该电路结构简单、性能稳定,线性度好,输出电流通过0-5V模拟电压调节,输出电压可达1100V,适合用作中高压化成箔到达电压的测试电源.文中还给出了利用该恒流源电路构成四通道高压化成箔时间电压自动测试仪的硬件方案. 相似文献
2.
宋荣 《深圳职业技术学院学报》2009,8(3):11-14
介绍一种以运算放大器为核心器件,通过NPN型三极管集电极输出的高压小电流精密恒流源电路,分析了电路的工作原理、重要元件的参数选择及电压检测电路带来的电流误差,给出了以运算放大器比例运算电路实现补偿的方法．该电路结构简单、性能稳定、线性度好,输出电流通过0-5V模拟电压调节,输出电压可达1100V,适合用作中高压化成箔到达电压的测试电源．丈中还给出了利用该恒流源电路构成四通道高压化成箔时间电压自动测试仪的硬件方案． 相似文献
3.
基于阈值电压的负温度特性以及热电压的正温度特性,给以适当的权重后把它们相加,提出了一个零温度系数的基准电压电路。该器件由工作在亚阈值区的CMOS晶体管组成,不包含电阻和双极晶体管。采用3支路电流基准结构替代共源共栅结构和嵌入式运算放大器,具有芯片面积小和功耗低的优点。仿真结果表明,在标准0.18μmCMOS工艺下,该电路可在0.75 V电源电压下工作,输出电压为563 mV。在-40~125℃范围内,电压温度系数仅为17.5×10^-6/℃。电源电压范围在1.2~1.8 V时线性灵敏度为569.5×10^-6/V,电源抑制比可达到66.5 dB@100 Hz,最高功耗仅为187.4 nW。 相似文献
4.
蔡顺燕 《四川教育学院学报》2014,(11):110-113
设计了一种输入电压为5.5V～25V,输出电压为5V的直流稳压电源及其漏电保护装置系统.直流稳压电源模块采用达林顿管TIP42、OP07运算放大器及三极管构成一个深度负反馈稳压电路.输出电压经ADS1286转换为数字量后送入单片机采样输出电压,经霍尔电流传感器CSM002A、跟随器OP07后,送入ADS1286,转换为数字量后送入单片机采样负载电流.由软件程序计算功率,并在液晶上显示.通过采样负载电流与总电流的差值实现漏电检测,并进行漏电保护.经测试,系统电压调整率Su≤1％,负载调整率SL≤1％,5.5V ～ 25V输入,输出为5±0.05V. 相似文献
5.
6.
《洛阳师范学院学报》2016,(11)
本文以STC12C5A60S2单片机为主控制器,设计了一种带漏电保护功能的线性直流稳压电源.电源主电路利用TL431产生2.5V基准源,将输出电压反馈过来和基准源比较,控制TIP127三极管导通,实现稳压输出.单片机首先利用10位内置ADC对输出电压、电流信号采集,然后完成相应的保护功能,最后将各参数送LCD显示.测试结果表明,该电源工作可靠、性能良好、稳定电压稳定,且输出电流可大于1A,电压调整率、负载调整率均在理想的范围之内. 相似文献
7.
在应用TL回路的原理分析跨导线性环电流放大器的基础上,以电压模电路的分析方法,推导了跨导线性环电流放大器频率特性的表达式,证实了跨导线性原理关于增益表述的正确性,以及该电流放大器具有较高上限截止频率的论述。在推演过程中说明了该放大器为理想电流放大器,其输出电流iod≈ion,从而克服了电压模电路中的密勒效应。输入为电流源激励,即输入端呈现低阻特性。正因为跨导线性环电流放大器具备这些特性,才使得它在高速、宽带集成电路中得到广泛的应用。 相似文献
8.
林蔚 《Journal of Zhangzhou Technical Institute》2008,10(2):8-12
本文设计的轨对轨运算放大器主要是为TFT-LCD的驱动电路提供驱动电压,输入采用电流补偿稳定运算放大器在整个输入共模范围内的跨导,采用AB类的输出方法提高运算放大器的输出范围,并对典型性能及参数进行仿真分析。 相似文献
9.
实现了一种基于CMOS工艺的用于DRM与DAB数字广播射频调谐器的具有低相位噪声与低功耗的工作在37.5MHz的差分结构晶体振荡器.在晶体振荡器的核心部分采用了PMOS晶体管来代替传统的NMOS晶体管以降低相位噪声.采用了对称结构的电流镜以提高直流稳定度.采用了由一阶CMOS运算跨导放大器和简单的幅度探测器构成的幅度探测电路以提高输出信号的电流精确度.芯片采用0.18-μmCMOS工艺实现,芯片面积为0.35mm×0.3mm.芯片包含用于驱动50Ω测试的负载接口电路,在1.8V供电电压下,所测得的芯片功耗仅为3.6mW.晶体振荡器的工作输出信号在距离其中心频率37.5MHz频偏1kHz处的相位噪声为-134.7dBc/Hz. 相似文献
10.
提出了一种结构新颖的亚阈值MOSFET电流模基准电路,利用反馈技术产生偏置于电流ICTAT的电流IPTAT,输出基准电压只是一个自变量（ICTAT）的函数,降低了其温漂系数．对电路进行了仿真,获得了较好的性能指标,这种电路结构在[-20℃～100℃]温度范围内对输出基准电压进行很好的高阶温度曲率补偿,能够获得很低的温漂系数（TC｜TT约6．25ppm／℃）,最小工作电压不大于1V． 相似文献
11.
Ying Zhan Zi Yan Zhi Hong Wan Xiang Wang Ye Zeng Min Yang Lan Yang 《British journal of educational technology : journal of the Council for Educational Technology》2023,54(4):817-835
Online peer assessment (OPA) has been increasingly adopted to develop students' higher-order thinking (HOT). However, there has not been a synthesis of research findings on its effects. To fill this gap, 17 papers (published from 2000 to 2022) that reported either a comparison between a group using OPA (n = 7; k = 22) and a control group or a pre–post comparison (n = 10; k = 17) were reviewed in this meta-analysis. The overall effect of OPA on HOT was significant (g = 0.76). Furthermore, OPA exerted more significant effects on convergent HOT (eg, critical thinking, reasoning and reflective thinking; g = 0.97) than on divergent HOT (eg, creativity and problem-solving; g = 0.38). Reciprocal roles and anonymity were found to positively moderate the impacts of OPA on HOT, although their moderating effects were not statistically significant because of small sample size of studies in the analysis. The results of the meta-analysis reinforce the arguments for regarding OPA as a powerful learning tool to facilitate students' HOT development and reveal important factors that should be considered when adopting OPA to enhance students' HOT.
Practitioner notes
What is already known about this topic- Online peer assessment (OPA) has significant positive impacts on learning achievement.
- OPA has been regarded as a potential approach to cultivating students' higher-order thinking (HOT) but has not been proved by meta-analysis.
- OPA should be carefully designed to maximise its effectiveness on learning.
- OPA has been proved to significantly positively influence students' HOT via meta-analysis.
- OPA exerted more significant effects on convergent HOT than on divergent HOT.
- The potential of reciprocal roles and anonymity for moderating the impacts of OPA on HOT should not be underestimated.
- OPA could be a wise choice for practitioners when they help students to achieve a balanced development of HOT dispositions and skills.
- Students' divergent HOT can be encouraged in their uptake of peer feedback and by allowing them autonomy in deciding assessment criteria.
- OPA with design elements of reciprocal roles and anonymity has great potential to promote students' HOT.
12.
A novel current-source active power filter(APF)based on multi-modular converter with carrier phase-shifted SPWM(CPS-SPWM)technique is proposed.With this technique,the effect of equivalent high switching frequency converter is obtained with low switching frequency converter.It is very promising in current-source APF that adopt superconducting magnetic energy storage component. 相似文献
13.
INTRODUCTION iout = i1 (4) Active power filter (APF) (Grady et al., 1990) The resulting iout is sinusoidal and high quality.is a power conversion system for compensating the In this way, APF could provide the harmonic cur-harmonic and reactive power from the nonlinear rent, which is an essential requirement of theload.… 相似文献
14.
Parameters optimization and nonlinearity analysis of grating eddy current displacement sensor using neural network and genetic algorithm 总被引：1，自引：0，他引：1
A grating eddy current displacement sensor （GECDS） can be used in a watertight electronic transducer to realize long range displacement or position measurement with high accuracy in difficult industry conditions. The parameters optimization of the sensor is essential for economic and efficient production. This paper proposes a method to combine an artificial neural network （ANN） and a genetic algorithm （GA） for the sensor parameters optimization. A neural network model is developed to map the complex relationship between design parameters and the nonlinearity error of the GECDS, and then a GA is used in the optimization process to determine the design parameter values, resulting in a desired minimal nonlinearity error of about 0.11%. The calculated nonlinearity error is 0.25%. These results show that the proposed method performs well for the parameters optimization of the GECDS. 相似文献
15.
INTRODUCTION With the development of modern electronics,there is a growing trend of designing a low-voltagehigh precision current reference in many mixed-signaland analog circuits such as data converters (Mehr andSinger, 2000; Oh et al., 2004), oscillators and PLLs(Razavi, 2001; Banba and Shiga, 1999). Low-costreasons need the reference to be realized in simplestandard CMOS logic process technology, withoutresorting to the use of BiCMOS process and specialdevices such as floating-g… 相似文献
16.
一体化电子式电流电压互感器研究 总被引：7，自引：1，他引：7
A high-performance current and voltage measurement system has been developed in power system.The system is composed of two parts:one current measurement element and one voltage measurement element.A Rogowski coil and a capacitive voltage divider are used respectively for the line current and voltage measurements.Active electronic components are used to modulate signal,and power supply for these components is drawn from power line via an auxiliary current transformer,Measurement signal is transmitted y optical fibers,which is resistant to electromagnetic induction and noise,With careful design and the use of digital signal processing technology,the whole system can meet 0.5% accuracy for metering and provides large dynamic range coupled with good accuracy for protective relaying use. 相似文献
17.
A novel software implementation for current polarity detection and current compensation is presented. For a three-phase zero-voltage soft-switching （ZVS） PWM converter based on phase and amplitude control （PAC）, when saw-tooth carriers with alternate positive and negative slopes are adopted, the positive or negative slopes are chosen according to the phase current polarity. Since polarity reversal causes current distortion, current at the instant of reversal should be compensated for. Based on the characteristic of unity power factor converter in rectification and regeneration modes, a software implementation for current polarity detection is proposed. Distortion of current zero-crossing caused by using saw-tooth carriers with alternate positive and negative slopes is analyzed, and the relevant compensation method is proposed. Experimental study with a 1.5 kW device shows that phase current has a small harmonic content and power factor is high both in rectification and regeneration modes. 相似文献
18.
In the hostile and highly corrosive marine environment,advanced composite materials can be used in marine current turbines due to their high strength-to-weight ratios and excellent resistance to corrosion.A composite material marine current turbine(CMMCT),which has significant advantages over traditional designs,has been developed and investigated numerically.A substantial improvement in turbine performance is achieved by placement of a duct to concentrate the energy.Computational fluid dynamics(CFD) results show that the extracted power of a ducted CMMCT can be three to four times the power extracted by a bare turbine of the same turbine area.The results provide an insight into the hydrodynamic design and operation of a CMMCT used to shorten the design period and improve technical performance. 相似文献
19.
A new type of fault current limiter (FCL) based on triggered vacuum switch (TVS) is proposed in this paper. The TVS-based
FCL (TFCL) is mainly composed of a capacitor, a current-limiting reactor connected with a capacitor in series and a TVS connected
with a capacitor in parallel. With the TVS at off or on state, the whole TFCL behaves as a conventional series compensator
or a fault current limiter, respectively. Numerical simulation and prototype experiment based on LC resonant test circuit
show that it is feasible to develop TFCL.
Supported by the Foundation of Chen-guang Project of the Wuhan Municipal Commission of Education 相似文献
20.
郭佳莉 《泉州师范学院学报》2014,(2):36-39
用邻苯二甲醛（OPA）、N-乙酰-L-半胱氨酸为衍生试剂对天冬氨酸对映体进行柱前衍生．采用ZORBAX Eclipse AAA4．6×150mm,5μm色谱柱,以0．05mol／LpH5．08的醋酸钠溶液与甲醇按57：43体积比作为流动相,流速0．5mL／min,柱温40℃下,考察高效液相色谱柱前衍生化法分离测定天冬氨酸对映体的效果．结果显示：在3．5min内分离出天冬氨酸对映体．在20～100nmol／mL线性范围内,线性关系良好,相关系数在0．99915以上,相对标准偏差在0．65％～1．70％之间．该法快速、简便、分离度高,能够完全分离DL-天冬氨酸对映体,并对其他氨基酸对映体的分离有良好的参考价值． 相似文献