一种用于无源RFID标签芯片的可校准低功耗基准源

提出一种应用于RFID芯片的低功耗、可校准基准源电路。设计采用了全MOS管以及电阻来实现,大部分管子都工作在亚阈值状态,同时可以产生基准电压和基准电流。该基准源采用了GSMC 0.13 μm 1P5M工艺来实现,其最大工作电流不超过350 nA,供电电压为1.2 V,并且在0.9 V~2.5 V电压下均可工作。在-45℃~65℃的工作温度下,电压基准源的温度系数为30.3 ppm/℃,电流基准源的温度系数为20.7 ppm/℃。     

一种1．03ppm／℃的高阶补偿带隙基准源

在曲率补偿方面。采用一种基于电阻匹配的核心电路结构。采用第二个运放产生一个负温度系数的电流来增强曲率补偿．同时把该负温度系数电流与核心基准源电路产生的正温度系数电流求和得到一个与温度无关的电流给运放提供偏置电流。这将提高运放和基准源的鲁棒性。该电路采用0．35umCMOS工艺实现,典型条件下仿真结果表明,在-40-125℃范围内温度系数为1．03ppm／℃电源电压只需大于1．25V便得到1．205V的稳定输出电压。     

一种新型的低温度系数基准电流源

针对目前集成电路中对高精度基准电流模块的高度需求,通过采用曲率补偿技术,设计了一种低温度系数(TC)的电流基准源;电路基于0.6um BiCMOS工艺,采用独特的设计方法,很好地利用了NPN、PNPBJT的温度特性;通过Hspice仿真和测试结果表明,在-45～85℃的温度范围内,该电路输出的基准电流温度系数为84.4ppm/℃。     

0.7V,11ppm/℃,纳瓦功耗的基准源

介绍了一种简单的高性能基准源电路．该电路利用了工作在饱和区和亚阈值区的MOS晶体管迁移率和阈值电压温度特性进行补偿，此外还利用二极管反相偏置电流的温度特性来改进电路的高温段的特性。使用HSPICE进行模拟，结果表明在电源电压为0．9V，温度在？20℃至120℃之间变化时，输出的基准电压为525mV，温度系数为11ppm／℃，功耗只有736nW。该电路电源电压可低至0．7V。电源噪声频率为1kHz时的电源抑制比为？48dB。     

一种新颖的受工艺参数影响较小的基准电流源

针对传统电流源受工艺参数影响较大的问题,提出了一种利用电压差平方电路来解决这个问题的思路;设计了一种新颖的受工艺参数影响较小的基准电流源电路,该电路采用0.6μm的BiCMOS工艺设计,利用Hspice进行仿真验证;结果表明,该电路在典型边界条件下-40℃~85℃范围内输出基准电流温度系数为17ppm/℃,变化率约0.2%,在6种不同边界条件下输出基准电流变化约为±1.72%。     

全CMOS温度补偿的参考电压电流源

提出了一种新型全CMOS温度补偿的参考电压和参考电流源结构,基于迁移率与阈值电压相互补偿的机制,产生一个与温度无关的电流参考源,再使输出电流流入一个与温度无关的有源负载,从而得到一个与温度无关的电压参考源。在-50℃-150℃的宽温度范围内,获得的参考电压源的温度系数为7.2ppm/℃,参考电流源的温度系数为22.7ppm/℃。     

一种高精度基准源电路

基于90 nm CMOS标准工艺,设计了一种低温漂的带隙基准源电路.一种结构新颖的温度曲率校正电路被采用,作为一级温度补偿电路的曲率校正电路.Hspice仿真结果表明:所设计电压源在温度-20℃～+120℃范围内,平均温度系数约为2.2 ppm/℃,获得了一个低压高精度的带隙基准电压源.     

带曲率补偿的带隙基准电流源的设计

简单介绍了带隙基准源的基本原理,给出了一款基于Widlar结构的带曲率补偿的带隙基准电压电流源的设计方法,通过采用TSMC₀.5μm工艺库对电路进行仿真,在-40～150℃的温度范围内,其带隙基准的输出具有12ppm/℃的温度系数,电流基准的输出具有42ppm/℃。此外,文中还对曲率补偿电路的工作原理进行了分析,并且通过仿真波形对曲率补偿的工作机制进行了讨论。     

高精度低温度系数带隙基准电压源的设计

基于0.5μm双层多晶双层铝CMOS工艺,采用共源共栅电流镜结构和基极电流补偿方法,设计了一种新颖的高性能带隙电压基准.结果表明,在温度-25℃～125℃范围,基准电压温度系数为15.3×10-6V/℃,低频时,电源抑制比可达-80db.该电路可做为A/D和D/A转换器中的基准电压源.     

一种新型的nA量级CMOS基准电流源

设计了一种新型的、不随电源电压变化的、温度系数很小的nA量级CMOS基准电流源,并分析了该电路的工作原理。该基准电流源不需要使用电阻,大大节省了芯片的面积。基于TSMC 0.18μmCMOS厚栅工艺,使用Spectre对电路进行了仿真。仿真结果表明,在输出基准电流为46 nA的情况下,该电路的温度系数为24.33 ppm/℃,输出电流变化率仅为0.028 9%/V,电源抑制比(PSRR)最高可达-85 dB,电路消耗的电流小于200 nA。     

EXCEL中的单元格引用剖析

EXCEL是数据处理软件中最出色的一款电子表格制作软件。电子表格是众多的排成行和列的单元格的集合,要对电子表格中的数据进行计算、分析和处理,就必须对单元格进行引用,如何引用单元格,以满足不同的实际问题的需要,是本文探讨的问题。文中研究了三种单元格的引用方式,并给出了应用实例。     

Reference in 160 Characters or Less: The Role of Text Messaging in Virtual Reference Services

This study focuses on how and why academic library patrons choose text message reference, particularly when other mediums are available. Researchers evaluated three years of text reference data to assess the peak usage times, types of questions received, the number of unique and repeat users, and the complexity of questions. Our analysis of data shows that text reference can fill a role within virtual reference services. We further identify reasons why text message services have not seen greater use, including students’ lack of awareness, limitations of the medium, and patron satisfaction with other modes of reference.     

The Virtual Librarian and the Electronic Reference Interview

ABSTRACT

For many students, the World Wide Web is their main access point for library research and, therefore, libraries need to find a venue for the virtual reference interview. This paper discusses the use of the library home page as a reference tool and its importance in the online reference interview process. This article also discusses some of the research that went into the creation of a home page for a large, urban, academic institution, how this research was utilized, and how the resulting page serves as an online surrogate for the in-person reference interview.     

Using the World Wide Web for Art and Humanities Reference Services

Abstract

This paper describes what the World Wide Web is and what is needed in order to access its information. It discusses the future of art and humanities reference resources and presents criteria for evaluating Web sites. A review of the literature related to “Generation X” and their information expectations was done. There is an annotated list of specific World Wide Web resources related to African Diaspora, American Poetry, Comparative Literature, Gay and Lesbian Literature, and Outsider Art. This list provides examples for evaluation and is not meant to be exhaustive.     

Developing a Chat Reference Training Program

ABSTRACT

In the last few years, chat reference services have been implemented by public, college and university libraries. One important aspect of the chat reference service is library staff training. Literature shows that this is a vital step in offering a chat reference service. Library staff need to be well-trained in areas of chatting, reference interviewing in a digital environment and using electronic resources, such as the Internet and databases. This article discusses the chat reference training program at the University of Nevada, Las Vegas. The following text provides an outline for establishing a chat training program including planning, organization, implementation and assessment. Areas of discussion include the chat reference interview, chatting and patron management techniques.     

Twenty Years of Virtual Reference

ABSTRACT

In observance of the twentieth anniversary of the publication of the first journal article devoted to virtual reference, the author explores early e-mail and chat reference services.     

As I Sit Studying: WWW-Based Reference Services

Abstract

This article reports on the current state of reference services on the World Wide Web (WWW). It explains what a WWW-based reference service is, describes several models of handling requests, and explores the impact of these services on traditional reference services. Based upon anecdotal information the author concludes that, to date, Web-based reference services have had little impact upon traditional reference services.     

A Historical Overview of Internet Reference Services for Distance Learners

SUMMARY

The advent of library services and collections on the Internet revolutionized reference services to students enrolled in distance learning programs. Prior to the Internet, reference librarians who supported distance learning programs had few methods, and many of them costly, to provide the equivalent library services advocated by the ACRL Guidelines. Through the Internet, these librarians were able to approximate the services and resources that had always been available to students who came into the library. This article describes the development of reference services on the Internet in a variety of libraries that support distance learners.     

Chat Reference

ABSTRACT

Internet Reference Services Quarterly is introducing a new column that will focus on current developments and practice concerns in chat reference. This first entry gives some background on the column's origins, and details the directions it will take.