一种用于16位Σ-Δ A/D转换器的跨导放大器

介绍了一种采用0.5μm CMOS工艺的轨到轨输入共栅共源带输出阻抗增强结构的跨导放大器电路。该放大器用在一个8倍过采样率,输出速率500 kps的16位二阶Σ-Δ加流水线型结构的A/D转换器中,位于Σ-Δ环路的第一级,完成过采样、相减求差和残差放大的功能,是整个A/D转换器的重要模拟电路单元。在5 V电源电压下,该放大器的仿真结果为直流增益大于90dB,单位增益带宽大于100 MHz,相位裕度大于75°。     

12位100 MS/s流水线A/D转换器的参考电压缓冲器

分析了参考电压精度对流水线A/D转换器性能的影响,并通过Matlab建模仿真,得到了12位流水线A/D转换器对参考电压精度的要求,即参考电压精度要达到10位以上.提出了一种新型的参考电压缓冲器结构,通过增加两个静态比较器,有效地提高了缓冲器的精度.采用SMIC 0.35 μm 3.3 V CMOS工艺,为一个12位100 MHz采样频率的流水线A/D转换器设计了电压值为1.65 V±0.5 V的参考电压输出缓冲器.Hspice后仿真结果显示,各个工艺角下,缓冲器可将干扰对1 V的差分输出的影响控制在0.35 mV以内.该缓冲器可以达到10位以上精度,能够满足12位100 MS/s流水线A/D转换器的设计要求.     

补偿流水线A/D转换器级间增益误差的后台校正技术

在分析流水线A/D转换器中残差放大器电容匹配性和运放的有限增益引起的误差对信号传输影响的基础上,基于冗余位校正流水线A/D转换器结构,通过在信号通路中加入由伪随机码控制的校正信号测量上述误差的方法,在后台校正输出数字信号中的级间增益误差。通过Mat-lab对A/D转换器进行了系统级仿真。结果表明,12位A/D转换器系统的SFDR提高了31.8dB,SNDR提高了11.5 dB,INL减小了3.43 LSB,DNL减小了0.21 LSB。     

一种用于10位50 MS/s流水线ADC的MDAC

利用运放共享技术,设计了一种用于10位50 MS/s流水线ADC的增益D/A转换器(MDAC).采用SMIC 0.25 μm 1P5M标准数字CMOS工艺,整个MDAC模块的版图面积为0.064 mm2.仿真结果表明,在50 MHz采样率下、输入信号为2 MHz(1.5 V振幅)正弦波时,整个电路模块的功耗为7.12 mW.     

采用分段平移技术校正流水线A/D转换器级间增益的方法

分析了流水线A/D转换器采样电容与反馈电容之间的增益失配,探究了运放有限增益与流水线残差输出及A/D转换器输出的关系,建立了精确的系统模型。通过建立14位流水线A/D转换器Verilog-A的行为级模型,在数字域对流水线A/D转换器输出数字码进行分段平移。在第一级级间增益误差达到±0.012 5时,校正前信噪比仅为62 dB,校正后信噪比提升到85 dB。提出的校正方法可有效补偿由流水线级间增益导致的数字输出不连续和线性度下降。     

并行分时流水线A/D转换器系统级研究

基于并行分时A/D转换器的理论研究,对该类型A/D转换器进行了系统行为级设计和仿真。分析了系统中并行误差及流水线A/D转换器等误差源对整个系统性能的影响。通过计算机仿真,给出了系统模块的设计参数。通过理论分析与系统仿真,为并行分时流水线A/D转换器的设计提供了理论依据和数据参考,为该类型A/D转换器提供了设计优化方向。     

一种消除电路"记忆效应"的数字域校正算法

基于"运放共享"电路工作原理,研究了流水线A/D转换器的MDAC模块因采用"运放共享"结构引入的"记忆效应";搭建实际电路,测试出"记忆效应"因子;采用Matlab,仿真了此效应对12位100 MHz流水线A/D转换器各项指标的影响.提出了一种基于FIR数字滤波器的校正算法,在数字域校正模拟电路中由于电容的非理想因素导致的误差.输入为1 MHz正弦波信号时,仿真结果表明,经过数字后台校正后,SFDR为91 dB,SNR为71 dB,流水线A/D转换器系统的指标有了大幅度的提升.     

9位100 MSPS流水线结构A/D转换器的设计

提出一种采用三级流水线型结构的9位100 MSPS折叠式A/D转换器,具体分析了其内部结构。电路使用0.6 μm Bipolar工艺实现, 由5 V/3.3 V双电源供电, 经优化设计后, 实现了9位精度,100 MSPS的转换速度,功耗为650 mW,差分输入范围2.2 V。给出了在Cadence Spectre的仿真结果,讨论了流水线A/D转换器设计的关键问题。     

12位50 MHz流水线ADC采样保持电路实现

对采样保持电路进行研究,对增益提高的运算放大器进行2阶系统模拟,得到最佳设计参数;提出一种栅压自举开关电路结构;设计了一个用于12位50 MHz流水线A/D转换器的采样保持电路.采用SMIC 0.35 μm混合CMOS工艺,对整个A/D转换器进行实现.测试结果表明,采样保持电路完全满足设计要求.     

一种高速低压用增益增强型运算跨导放大器设计

设计了一种全差分增益增强CMOS运算跨导放大器,用于12位100 MHz采样频率的流水线A/D转换器。详细分析了辅助运放产生的零极点对,优化了建立时间。电路采用中芯国际（SMIC）0.18μm混合信号CMOS工艺设计, 1.8 V电压供电。仿真结果表明,运算放大器的开环增益为102 dB,在3pF负载电容下单位增益带宽为1.27G,精度为0.01%时的建立时间为4.3 ns。     

一款切合实际的30A能量计

本文介绍了一款集成了30A检测电阻器LTC2947.     

注钼纯铝的研究

利用从金属蒸汽真空弧离子源（简称ＭＢＶＶＡ源）引出的强束流钼离子对纯铝进行了不同束流密度的离子注入。加速电压为４８ｋＶ，剂量为３×１０￣（１７）ｃｍ￣（－２），束流密度为２５和４７μＡ·ｃｍ￣（－２），Ｘ衍射分析证明在注入层内可形成Ａｌ＿（１２）Ｍｏ晶体，背散射（ＲＢＳ）分析证明Ａｌ＿（１２）Ｍｏ的厚度可达６００至７００ｎｍ。     

A Nyquist-rate delta-sigma A/D converter

This paper describes an analog-to-digital converter which combines multiple delta-sigma modulators in parallel so that time oversampling may be reduced or even eliminated. By doubling the number of Lth-order delta-sigma modulators, the resolution of this architecture is increased by approximately L bits. Thus, the resolution obtained by combining M delta-sigma modulators in parallel with no oversampling is similar to operating the same modulator with an oversampling rate of M. A parallel delta-sigma A/D converter implementation composed of two, four, and eight second-order delta-sigma modulators is described that does not require oversampling. Using this prototype, the design issues of the parallel delta-sigma A/D converter are explored and the theoretical performance with no oversampling and with low oversampling is verified. This architecture shows promise for obtaining high speed and resolution conversion since it retains much of the insensitivity to nonideal circuit behavior characteristic of the individual delta-sigma modulators     

A charge-domain D/A conversion system

In this article, a new multiplication type D/A conversion system using CCD is proposed and the result of simulations for evaluating its performance is reported. The system consists of a recursive charge divider which divides input charge-packet Qin sequentially into output charge-packets Qin · 2^-i and two charge-packet accumulators which accumulates output charge-packets from the recursive divider selectively according to digital input signal bits starting from MSB. The system converts input digital signal bit by bit, fully in charge-domain, thus the power consumption for this system is supposed to be very low. Also in this article, an effective method to achieve higher accuracy for splitting a charge-packet into two equal-sized packets using very simple hard-ware structure is proposed. As the result of simulations, we have found that the upper limit of accuracy for the conversion is determined by transfer efficiency of CCD, and within this range a trade-off relationship exists among conversion-accuracy, circuit-size and conversion-rate. This unique relationship enables to reduce the circuit size of D/A converter significantly maintaining the accuracy of conversion by slowing down the conversion-rate. This D/A converter is appropriate especially for the system integration because of its simple structure, tolerance to the fabrication error and low power consumption inherrent in the nature of CCD. By using of this system, it is expected to be possible to realize a focal plane image processor performing parallel analog operations such as DCT conversion with CCD imager incorporated on the same Si chip by the same MOS process technology.     

A monolithic video A/D converter

The design and measured performance of a fully parallel monolithic 8-bit A/D converter is reported. The required comparators and combining logic were designed and fabricated with a standard high-performance triple-diffused technology. A bipolar comparator circuit giving good performance with high input impedance is described. Circuit operation is reported at sample rates up to 30 megasamples per second (MS/s), with analog input signal power at frequencies up to 6 MHz. Full 8-bit linearity was achieved. An SNR of 42-44 dB was observed at input signal frequencies up to 5.3 MHz.     

高速高精度A/D转换器

本文介绍了用于观测太阳磁场的天文望远镜系统的高速高精度局部级联式多阈值A/D转换器。文章着重讨论了,为实现高速、高精度所采用的技术要点,并提出了研制高速高精度A/D转换器所必须考虑的有关问题。 我们所研制的A/D转换器,分辨率为1mV,相对误差0.025％,字长12位,前面接采样保持电路后,速度为10万次/秒。     

A charge-balancing monolithic A/D converter

The quest for a minimum-parts-count DPM led to the development of this monolithic, low power analog-to-digital converter. It incorporates the analog and digital functions historically implemented separately with specialized process technologies into a chip with full /spl plusmn/3 digit accuracy. The integration of resistors, compensation capacitors, and an oscillator reduces the external component complement to three capacitors and one adjustable reference. TTL compatible outputs include sign, overrange, and under range information in addition to the three digit strobes and the BCD data outputs. The logic operates between +5 V and ground, the linear section between +5 V and -5 V. The paper describes the conversion algorithm and its CMOS implementation, emphasizing the analog design of this innovative device.     

A Convenient Multivariate Gram-Charlier Type A Series

It is often necessary to approximate the probability density function of a random variable from given statistical moments. The Gram-Charlier Type A series is one well known method for such representations. In this note, the Gram-Charlier Type A series is generalized to the multidimensional case.     

一种识别说话者的新方法

在能够自动识别视频中的说话者的系统中,大部分采用的是声音和唇部运动相结合的方法。文中则采用了另一种方法有效地达到了目的,即通过检测人体头部和手部的运动来鉴别说话者。基于演讲者在说话时通常会伴有头部运动或是手部运动,该方法既能实现说话者的检测,又能避免由于观测点过远而导致无法判断人唇部运动的局限性。在系统的实施过程中,运用了多种图像处理方法,并且对三帧差运动法做出了改善,使其能更高效、更准确地检测到头部和手部的运动。经过多个不同的视频测试后,本系统的F1 score高达91．91％,从而验证了该系统的可行性。     

没有管理者的密钥共享方案

一般的密钥共享方案中都假设有一个管理者,管理者的作用是分发密钥,因此对管理者的可信要求很高,而现实生活中很难找到符合要求的管理者.文中利用单调存取结构上的张成方案构造了一个没有管理者的密钥共享方案,并证明其是一个可行的实用的密钥共享方案.基于这个的方案,构造了一个分布式密钥生成器.