Performance degradation of APD-optical receivers due to darkcurrent generated within the multiplication region

General expressions for the effective gain and effective excess noise factor associated with dark current generated within the high-field region of an avalanche photodiode (APD) are given. The influence of this background current on the performance of a uniformly multiplying APD receiver is evaluated and compared with that due to a dark current component generated outside the multiplication region (diffusion current). The results indicate clearly that the former dark current component has less effect on receiver performance than the latter, especially when hole and electron ionization rates are very different     

A high-speed differential CMOS Schmitt trigger with regenerative current feedback and adjustable hysteresis

This paper presents a brief overview of Schmitt triggers and proposes a new differential current-feedback Schmitt trigger. The hysteresis of the proposed Schmitt trigger is generated using regenerative current feedback and can be adjusted by varying the current of the regenerative feedback network. The center of the hysteresis can also be adjusted by varying the common-mode input voltage. The proposed Schmitt trigger has the characteristics of current-mode circuits, making it particularly attractive for low-voltage high-speed applications. The proposed Schmitt trigger has been designed in TSMC-0.18 μm 1.8 V CMOS technology and analyzed using Spectre from Cadence Design Systems with BSIM3V3 device models. Simulation results are presented.     

Design techniques for ASK demodulators of passive wireless microsystems: a state-of-the-art review

This paper presents a brief overview of Schmitt triggers and proposes a new differential current-feedback Schmitt trigger. The hysteresis of the proposed Schmitt trigger is generated using regenerative current feedback and can be adjusted by varying the current of the regenerative feedback network. The center of the hysteresis can also be adjusted by varying the common-mode input voltage. The proposed Schmitt trigger has the characteristics of current-mode circuits, making it particularly attractive for low-voltage high-speed applications. The proposed Schmitt trigger has been designed in TSMC-0.18 μm 1.8 V CMOS technology and analyzed using Spectre from Cadence Design Systems with BSIM3V3 device models. Simulation results are presented.     

A note on photocurrents in extrinsic semiconductors

The absorption of light generates excess carriers (electrons and holes) in a uniformly doped semiconductor and sets up diffusion currents. Owing to the difference of the diffusion constants for electrons and holes, the diffusion currents produce a small electric field in a zero current configuration. This is well known. It is not realized generally that fairly large electrical currents of ten's of mA can be generated under short circuit conditions. Theoretical treatments of these effects in the literature are logically flawed. In this paper the situation will be remedied.     

Trigger Detection Using Geographical Relation Graph for Social Context Awareness

The concept of context awareness is believed to be a key enabler for the new ubiquitous network service paradigm brought by cloud computing platforms and smartphone OSs. In particular, autonomous context-based service customization is becoming an essential tool in this context because users cannot be expected to pick step by step the appropriate network services by manually and explicitly matching preferences for their current context. In this work, we hence focus on the core problem of how to detect changes of context for network services. In turn, detection of such changes can trigger timely system reconfigurations. We introduce a trigger detection mechanism based on a mixed graph-based representation model able to encode geographical and social relationships among people and social objects like stores, restaurants, and event spots. Our mechanism generates a trigger when a significant change in the graph takes place, and it is able to render significant changes in a geographical relationship that holds among objects socially connected with each other. The main benefits of our method are that (1) it does not require building reference models in advance, and (2) it can deal with different kinds of social objects uniformly once the graph is defined. A computer simulation scenario provides evidence on the expected performance of our method.     

Experimental study of the control characteristics of a Schottky-trigger electrode on a Gunn device

To clarify the condition for the generation of a high-field domain in a Gunn device equipped with a Schottky-trigger electrode, a detailed experimental study was carried out. The difficulties in such experiments had so far rested in the accurate evaluation of the potential difference between the trigger electrode and the semiconductor thereunder, which we solved by an equivalent circuit representation of the device. Moreover, the accuracy of the evaluation of the potential difference was further increased by making use of the critical condition for the forward current through the Schottky barrier of the trigger electrode. From the experimental results it was made clear that a high-field domain is not necessarily generated when the field in the channel under the trigger electrode reaches the threshold field, but some form of the over-threshold-field state is established before a domain is generated. This shows that the device could be biased to higher anode voltages, leading to higher output voltages and wider operational margines than had earlier been expected.     

一种脉冲振荡电路的分析与设计

采用开关元件控制的恒流充放电是产生稳定非正弦振荡波的主要方法。文章利用施密特(Schmitt)触发器为核心的状态延迟及转换元件，并采用恒流充放电技术，配合精确的时序控制，实现了一种高稳定的低功耗矩形波振荡电路。     

A discussion on the temperature dependence of latch-up triggercurrent in CMOS/BiCMOS structures

The measured temperature dependence of latch-up trigger currents in CMOS/BiCMOS structures from 10 to 125 °C is quantitatively discussed based on a simple lumped element equivalent model. Temperature coefficients of the p-well and n-well trigger currents for three different well structures are around -1.0%/°C and -0.6%/°C, respectively. The latch-up trigger currents calculated using temperature dependent parasitic parameter values such as the current gains of parasitic bipolar transistors, the forward emitter-base voltage, and parasitic well shunting resistances are in good agreement with the measured ones. In addition, the role each parameter plays in reducing latch-up trigger currents at higher temperature is clarified     

Differential CMOS Schmitt trigger with tunable hysteresis

This letter presents a new differential Schmitt trigger with tunable hysteresis. The hysteresis is generated using a cross-coupled inverter pair. The amount of hysteresis can be adjusted by varying the current of the symmetrical load. The proposed Schmitt trigger has been designed in TSMC-0.18 μm 1.8 V CMOS technology and analyzed using Spectre from Cadence Design Systems with BSIM3V3 device models. Simulation results demonstrate that the triggering voltage of the Schmitt trigger can be adjusted from 0.95 to 1.35 V approximately.     

Insight into multiple-triggering effect in DTSCRs for ESD protection

The diode-triggered silicon-controlled rectifier (DTSCR) is widely used for electrostatic discharge (ESD) protection in advanced CMOS process owing to its advantages, such as design simplification, adjustable trigger/holding voltage, low parasitic capacitance. However, the multiple-triggering effect in the typical DTSCR device may cause undesirable larger overall trigger voltage, which results in a reduced ESD safe margin. In previous research, the major cause is attributed to the higher current level required in the intrinsic SCR. The related discussions indicate that it seems to result from the current division rule between the intrinsic and parasitic SCR formed in the triggering process. In this letter, inserting a large space into the trigger diodes is proposed to get a deeper insight into this issue. The triggering current is observed to be regularly reduced along with the increased space, which confirms that the current division is determined by the parasitic resistance distributed between the intrinsic and parasitic SCR paths. The theoretical analysis is well confirmed by device simulation and transmission line pulse (TLP) test results. The reduced overall trigger voltage is achieved in the modified DTSCR structures due to the comprehensive result of the parasitic resistance vs triggering current, which indicates a minimized multiple-triggering effect.     

Xenon flashlamp triggering for laser applications

Results of an investigation into the triggering of linear xenon flashlamps are presented, with particular reference to xenon flashlamps in laser applications. Measurements are described which give information on the arc formation process, trigger voltage thresholds, peak trigger currents, lamp energy output stability, and electromagnetic interference (EMI) for both series and parallel triggering. Particular attention is given to the performance obtained with both the correct and the incorrect polarities for the two types of triggering. The investigation makes extensive use of a high-speed streak camera and a wideband (100 MHz) continuous sweep spectrum analyzer, as well as more conventional instrumentation. It was found that: 1) the triggering process is extremely fast (≤50 ns) for both methods, but that parallel triggering produces trigger currents which are 100 times smaller than series; 2) the trigger current rather than the main energy, discharge current is the dominant EMI source; 3) the measured RF spectra show the corresponding EMI superiority of parallel over series; and 4) the two methods are equivalent in regard to the effect on lamp efficiency and stability.     

Access control of data in integrated voice/data CDMA systems:benefits and tradeoffs

In previous work, access control for data has been proposed as a method to ensure adequate quality of service (QoS) in an integrated voice/data CDMA system. The motivation behind access control is to schedule data packet transmissions in slots when voice activity is low and to curtail data transmissions when the voice load is heavy. In this work, the class of probabilistic access control schemes, wherein data transmissions are controlled by dynamically changing the permission probability, are considered. The trigger for changing the permission probability is a measure of the current uplink load. Perfect power control is assumed first, and the trigger for access control is the power control feasibility condition, Schemes based on prediction are analyzed. While prediction schemes are complex to implement, they do provide an upper bound for performance of access control schemes. A simple and practical access control scheme, proposed earlier in the literature, is then extended. It controls the permission probability for data based on uplink load and a 1-bit broadcast feedback to all of the mobiles. The performance of this scheme depends on the choice of three parameters. It is demonstrated that, through a combined choice of these parameters, access control can be tuned to perform as desired and to yield significant capacity gains over not using access control. Results are then extended to the case of imperfect power control, where the outage criterion is based on limiting the total received power at the base station. In this case, too, the simple control scheme is shown to work well     

Modeling and analysis of transient latchup in double-well bulk CMOS

Characteristics of transient latchup due to noise excitation through the gate of a parasitic SCR are measured and described by a new simplified model to clarify latchup immunity in a double-well CMOS with a nonepitaxial substrate. The model accounts for the effects of high-level carrier injection and base transit delays of the two parasitic transistors, and it can describe the observed latchup transient faithfully if the model parameters are given according to the predetermined procedure. The noise-pulse-width dependence of the latchup trigger current is obtained as a function of current gain, transit time, and transistor base-emitter shunt resistance to show the last one most sensitive to the trigger current. The optimum parameters with the double well are deduced from study to relate the model to structural parameters.     

Moment-method determination of the surface currents and fields radiated by rectangular microstrip patch-antennas

A quantitative solution is presented of the surface currents and the corresponding fields generated in free space by electrically thin microstrip patch-antennas of rectangular configuration. Use is made of a versatile analytical tool known as the method of moments, in which the surface current density is approximated by a series expansion involving piece wise linear basis functions and weighted superposition coefficients which are to be determined. It is shown that when the governing integro-diflerential equations are reformulated in matrix form involving generalized network parameters, the desired current distribution emerges in a simple compact form. A remarkable feature of the result of the present analysis is the fact that the field induced in the substrate is due to a finite charge distribution rather than the previously implied phenomenon, viz. the influence of an infinite charge distribution. Indeed, the charge distribution responsible is directly derivable from the time-harmonic continuity equation. All numerical results displayed are based on the use of plane-wave irradiation and the paper includes a discussion of certain practical feed arrangements as well as some practical applications. Results are presented in graphical forms within the frequency limits 1157-1237 MHz for two different sizes of the conducting patch.     

A multibit test trigger circuit for megabit SRAMs

A multibit test (MBT) trigger circuit for megabit SRAM packages with no unused pins is discussed. The features of the MBT trigger circuit are a logic trigger mode without using any additional pins and practical use of counter circuits. The essence of trigger mode selection is that two pulses are for MBT set and three pulses are for MBT reset. In this way, a logic trigger mode that does not use NC pins is especially effective as a 4-Mb SRAM. In addition, the proposed scheme is able to act as a logic trigger for an MBT circuit. The scheme is simple and effective. The logic trigger mode is proposed for future standardization     

低谐波软启动器的研究

设计一种软启动器,以可控硅做主控元件,单片机控制软启动策略,实现对异步电动机的软启动。STM32系列微控制器通过控制可控硅导通的周期波数,进而改变异步电动机启动电压的平均值,从而减少启动电流对电网的冲击。同时进行相位检测,确定启动电流的过零触发,克服了一般软启动器产生严重谐波污染的问题。     

Simple approximation for Schmitt trigger characteristics

A formula is proposed for the input-output characteristic of a Schmitt trigger. Using a single parameter, the formula can fit a variety of practical Schmitt trigger characteristics.     

18V LDMOS器件ESD电流非均匀分布的模拟和测试分析

通过二维器件仿真,分析单指、多指18V nLDMOS器件在静电放电防护中电流分布的非均匀性问题。经仿真分析可知,寄生三极管的部分导通是单指器件电流分布不均匀的原因;器件的大面积特征、材料本身的不均匀性等因素导致叉指不同时触发,同时,由于nLDMOS各叉指基极被深N阱隔离,先被触发的叉指无法抬高未触发叉指的基极电位帮助其开启,是多指器件电流分布不均匀的原因。器件的TLP(Transmission line pulse)测试结果与仿真分析吻合,指长分别为50μm和90μm的单指器件ESD电流泄放能力分别为21mA/μm和15mA/μm;指长为50μm的单指、双指、四指和八指器件的ESD失效电流分别为1.037A、1.055A、1.937A和1.710A,不与指数成比例增大。     

一种非对称不变分布的混沌干扰源设计与干扰效果分析

提出了一种用于干扰数字通信系统的非对称不变分布的混沌干扰样式.基于混沌映射产生均匀分布的混沌序列,经过相应非线性变换,得到了服从非对称不变分布的混沌干扰信号.与现有干扰信号产生方法相比,该方法易于模块化实现,可控性和可再生性好.理论分析和仿真结果表明,相比于高斯分布干扰,满足Rayleigh分布的混沌干扰对QPSK和1...     

Electrostatic fields due to an electrode mounted on a conductingpad of finite extent in a planar stratified medium

The quasistatic fields generated by an electrode mounted on a perfectly conducting pad of finite extent and embedded in a planar stratified medium are analyzed. An integral equation in the spectral domain is derived for the outflowing current density distribution on the pad-electrode surface. The method of moments is then applied to solve the integral equation. The effects of the electric properties of the stratified medium and the standoff thickness on the total electrode current are investigated. Several conductivity profiles modeling different practical measurement environments are also considered