用一种新的补偿方法实现低压差线性稳压器

使用一种新的频率补偿方法设计了一种100 mA低压降CMOS线性稳压器(LDO).所设计的LDO仅使用了一个PMOS管进行补偿,无需使用电路内部其他的补偿电容和补偿电路就能保持稳定.使用0.18 μm工艺仿真结果表明,设计的LDO使用4.7 μF的负载电容,具有高的PSRR和很好的瞬态反应特性,在负载电流从0 mA跳变到100 mA以及从100 mA跳变到0 mA的时候,输出的变化小于8 mV,反应时间小于1μs,且在1kHz的时候PSRR为-72.3 dB.     

高PSRR超低噪声的LDO设计

便携式医疗电子设备在信号传输中易受到噪声干扰,为了抑制交流纹波对微小信号的影响,设计了一种高电源抑制比(power supply rejection ratio,PSRR)、超低噪声的低压差线性稳压器(low-dropout regulator,LDO)。利用电流缓冲和动态零极点追踪补偿技术来实现环路的稳定,同时也扩展了环路的单位增益带宽,提高了高频下的PSRR。稳压器采用两级结构,通过预稳压调制级加低通滤波器结构来实现低压差线性稳压器的超低噪声,且低通滤波器的截止频率有利于低频下PSRR的提高。基于5V-0.35μm CMOS工艺设计,采用cadence仿真软件进行仿真验证。仿真结果表明,在100kHz、10kHz、1kHz、100Hz频率下,PSRR分别可达到-66、-85、-96和-97dB。在不同的负载下,输出噪声在10Hz~100kHz频段不超过10μVrms,重载(250mA)时的输出噪声最低可达到7.5μVrms,可用于便携式医疗电子设备。     

一种低噪声高PSRR的LDO线性稳压器

介绍了 LDO线性稳压器的系统组成原理,分析了系统的电源电压抑制比(PSRR)以及噪声与电路结构的关系,在此基础上,对LDO的核心电路模块进行了设计,并基于0.5μm标准CMOS工艺,运用Cadence平台进行了模拟仿真和验证.测试结果表明:该LDO的PSRR最低约为-45 dB@1 MHz,最高约为-75 dB@217 Hz;输出电压噪声在10 Hz频率以下约为0.78 μV(P-P),在10 Hz至l00 kHz频率范围内约为0.1 μV(RMS),能满足低噪声和高PSRR应用的要求.     

一种高电源抑制比的CMOS带隙基准电压源

设计了一种采用前调整器的高电源抑制比的CMOS带隙基准电压源.基于CSMC 0.5 μm标准CMOS工艺,分别对有前调整器与没有前调整器的CMOS带隙基准电压源进行了设计与仿真验证.仿真结果显示,采用前调整器的带隙基准在100 Hz、1 kHz、100 kHz处分别获得了-117.3 dB、-106.2 dB、-66.2 dB的高电源抑制比,而没有采用前调整器的CMOS带隙基准在100 Hz、1 kHz、100 kHz处仅分别获得了-81.8、-80.1、-44.9 dB的电源抑制比;在-15 ～90℃范围内,采用前调整器的带隙基准的温度系数为6.39 ppm/℃;当电源电压在2.2 ～8 V变化时,采用调整器的带隙基准的输出电压变化仅9.73μV.     

LDO稳压器中动态频率补偿和限流保护的研究

.文章针对LDO稳定性的问题,提出了一种内部动态频率补偿电路,使LDO线性稳压器的稳定性不受负载电容的等效串联电阻的影响,其单位增益带宽也不随负载电流变化而改变,大大提高了瞬态响应特性;采用Hynix 0.5μm CMOS工艺模型对电路进行仿真;此外,该电路在实现动态频率补偿的基础上又加入了系统的过流保护功能,当负载电流大于限制电流时,LDO不能正常工作;当负载电流小于限制电流时,又自动恢复到正常工作状态。     

应用于眼压信号检测的低噪声前置放大器设计

基于SMIC 180nm CMOS工艺,设计并实现了一款应用于眼压信号检测系统的低噪声前置放大器.该放大器使用二极管连接的MOS管实现GΩ级别的大电阻,在反馈回路中该伪电阻与反馈电容并联在低频段产生高通截止点以抑制直流失调电压和低频噪声,达到较好的噪声性能.后仿真结果显示:低噪声前置放大器的直流增益为40dB,有效带宽从0.25Hz到46kHz,在低频频率100Hz处的等效输入噪声为197.3nVrms,采用1.8V的电压供电,核心电路功耗为32.4μW,芯片面积为0.75mm×0.62mm.     

一种用于光电标签的高电源抑制比的低压差线性稳压器设计

高电源抑制比低压差线性稳压器(LDO)采用UMC 0.18μm标准CMOS工艺进行流片,电路中采用偏置电流提升技术、偏置复用等技术来降低LDO的功耗.为保证LDO的稳定性,电路采用密勒补偿技术增强系统的相位裕度.同时,采用前馈结构来提高在低静态电流时LDO的瞬态响应.输入电压为光电池所提供的2 V电压,输出电压为1.8 V,该稳压器的最大负载电流约为13 m A.当负载电流为2 m A时,电源抑制比约为-67d B,其带宽在6 k Hz左右.稳压器的静态电流约为32.2μA,芯片面积为320×224μm~2.     

适用于OTA-C滤波器的高线性OTA的设计

设计了一种适用于OTA-C滤波器的高线性运算跨导放大器(OTA).该OTA采用新型的乘法器输入级,以获得大的线性跨导输入范围;采用一种新的共模负反馈(CMFB)策略,将主放大器输出电压线性压缩后再引入CMFB电路,以改善传统CMFB结构对OTA输出线性范围的限制.在SMIC.35 μm标准CMOS工艺下仿真,结果显示:输入级的线性跨导差分输入电压范围达到了—2～2 V,等效跨导在1 μS时,直流(DC)开环增益达到了76 dB,共模抑制比(CMRR)为140 dB,电源抑制比(PSRR)为144 dB.基于这种OTA设计了OTA-C二阶低通巴特沃斯滤波器.通过调节OTA的跨导,滤波器在1 pf的负载电容下的截止频率从11 kHz变化至419 kHz;当截止频率为100 kHz时输出为3 Vp-p@100 kHz时的总谐波失真(THD)为—47 dB.     

一种新型高电源抑制比的低压差线性稳压器

提出了一种新的基于前向通路结构的高电源抑制比（PSRR）的低压差线性稳压器（LDO）结构,具有全负载范围内PSRR高、通路对系统稳定性影响小、电流效率高等特点.采用chart 0.35μm 5 V CMOS工艺进行电路设计仿真.后仿真结果表明,全负载范围内最差线性调整率为633μV/V.1 kHz处PSRR为76 dB...     

一种高摆率低功耗无片外电容的LDO设计

本文介绍了一种低功耗的无片外电容快速响应的低压差线性稳压器(LDO),用于数字电路供电.该LDO采用电流型跨导运算放大器,克服了传统运算放大器摆率和静态电流之间的矛盾.提出了一种瞬态增强电路,既可以动态地调整误差放大器偏置,同时也能够直接对调整管栅极电压进行调节,增强了负载瞬态响应性能.该LDO基于28nm CMOS工艺,面积为55×42μm2.输入1.1V,压差约为100mV,最大负载电流50mA.静态电流为5μA,在负载电流变化率为49.9mA/μs的情况下,恢复时间为2.5μs,过冲电压和下冲电压均小于100mV.     

An Index mechanism for multi-scale view in spatial databases

There are numerous geometric objects stored in the spatial databases. An importance function in a spatial database is that users can browse the geometric objects as a map efficiently. Thus the spatial database should display the geometric objects users concern about swiftly onto the display window. This process includes two operations:retrieve data from database and then draw them onto screen. Accordingly, to improve the efficiency, we should try to reduce time of both retrieving object and displaying them. The former can be achieved with the aid of spatial index such as R-tree, the latter require to simplify the objects. Simplification means that objects are shown with sufficient but not with unnecessary detail which depend on the scale of browse. So the major problem is how to retrieve data at different detail level efficiently. This paper introduces the implementation of a multi-scale index in the spatial database SISP (Spatial Information Shared Platform) which is generalized from R-tree. The difference between the generalization and the R-tree lies on two facets: One is that every node and geometric object in the generalization is assigned with a importance value which denote the importance of them, and every vertex in the objects are assigned with a importance value,too. The importance value can be use to decide which data should be retrieve from disk in a query. The other difference is that geometric objects in the generalization are divided into one or more sub-blocks, and vertexes are total ordered by their importance value. With the help of the generalized R-tree, one can easily retrieve data at different detail levels.Some experiments are performed on real-life data to evaluate the performance of solutions that separately use normal spatial index and multi-scale spatial index. The results show that the solution using multi-scale index in SISP is satisfying.     

Perspherical Approaches for Electrons in Atoms and Charged Excitons in Quantum Wells

Instead of following Fock’s expansion,we solve the Schrodinger equation for some quantum mechanical manybody systems such as electrons in atoms and charged excitons in quantum wells in a similar way in hyperspherical coordinates by expanding the wave functions into orthonormal complete basis sets of the hyperspherical hannonics(HHs)of hyperangles and generalized Laguerre polynomials(GLPs)of the hyperradius.This leads the equation to     

Advances in broadband wireless communications under high-mobility scenarios

Future mobile communication systems aim at providing very high data transmission rates, even in high-mobility scenarios such as high-speed wheel-track trains, maglev trains, highway vehicles, airplanes, guided missiles or spacecraft. A particularly important commercial application is the strong and increasing worldwide demand for high- speed broadband wireless communications （up to 574.8 km/ h test speeds or 380 km/h commercial speeds） in railways, providing data, voice and video services for applications such as onboard entertainment services to passengers, train control, train dispatch, train sensor status handling and sur- veillance. In such high-mobility scenarios, there are a number of communication challenges, including fast hand- over, location updating, high-speed channel modeling, estimation and equalization, anti-Doppler spreading tech- niques, fast power control, and dedicated network architec- ture. Because signal transmission in very high-speed scenarios will inevitably experience serious deterioration, it is imperative to develop key broadband mobile communi- cation techniques for such high-speed vehicles.     

Wuhan University Journal of Natural Sciences TOTAL CONTENTS

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Scale-based spatial data model for GIS

Being the primary media of geographical information and the elementary objects manipulated, almost all of maps adopt the layer-based model to represent geographic information in the existent GIS. However, it is difficult to extend the map represented in layer-based model. Furthermore, in Web-Based GIS, It is slow to transmit the spatial data for map viewing. In this paper, for solving the questions above, we have proposed a new method for representing the spatial data. That is scale-based model. In this model we represent maps in three levels: scale-view, block, and spatial object, and organize the maps in a set of map layers, named Scale-View, which associates some given scales.Lastly, a prototype Web-Based GIS using the proposed spatial data representation is described briefly.     

英文诗歌中的喻类修辞

为了有助于提高英文爱好者的个人情操、文化素养和学习兴趣,以及专业人员对英语学习和研究进行多途径的探索,本文通过一些精选诗歌的引证和分析,着重论述了喻类修辞法在英文诗歌中的运用其及效果。     

Man Is Unable to Change the Miserable Life——Analysis of the Arrangement of Four Characters in The Glass Menagerie

Tennessee Williams is considered as one of the most important American playwrights since World War II.The Glass Menagerie is his first successful drama,which describes a tragic situation of family and means to say that Man is unable to change the miserable life,no matter whatever means he try,This essay focuses on the analysis of the arrangement of the four main characters:Laura.Amanda,Jim and Tom to reveal the theme.Laura is fragile.Amanda is brave.Jim is vital.Tom is sensible.And all of them develop and try the different means to struggle against life,but fail tragically.With the evidence,the paper comes to conclusion naturally that Man is unable to change the miserable life,and he dooms to fail.     

Characterization of root-nodulating bacteria on Retama raetam in arid Tunisian soils

The aim of this study is to investigate the diversity of Retama raetam root-nodule bacteria isolated from arid regions of Tunisia. Twelve isolates, chosen as representative for different 16S rRNA gene patterns, were characterized by 16S rRNA gene sequencing and phenotypic analysis. Isolates were assigned to Sinorhizobium, Rhizobium and Agrobacterium. Symbiotic properties of Sinorhizobium and Rhizobium isolates showed a large diversity in their capacity to infect their host plant and fix atmospheric nitrogen. Strain RK 22 identified as Rhizobium was the most effective isolate.     

An Affordable Accurate Evaluation of the Binding Conformations Predicted by Molecular Docking Studies in Bio-System

正Recently,docking has been widely used to predict the binding-modes of protein-inhibitors,when the crystal complexes structure was absent.Most docking algorithms are able to generate a large number of probable conformations,it,however,is difficult to effectively evaluate these docking poses and identify the most reasonable bindingmode.In the present study,on the basis of the crystallographic data of human 3-hydroxy-3-methylglutaryl coenzyme     

WIMAX与WI-FI技术分析及联合组网

介绍了WiMAX与Wi-Fi两种无线宽带接入技术,并对两者之间的关系及相互之间的影响做了对比及分析,并对WiMAX的关键技术进行了详细说明,最后对两者的联合组网方式做了简单的探讨。