Stability analysis of circuits including BJT differential pairs

In this paper, a necessary and sufficient condition for robust stability of electronic circuits at high frequency, which contain differential pair (emitter–coupled pair), is proposed. In fact, when emitter–coupled pairs are used as one input signal–one output signal, they have uncertainty in their transfer functions at high frequency. Even it is shown that this uncertainty can cause instability in closed loop electronic circuits at high frequency.The uncertainty is modeled as multiplicative perturbation in the transfer function of the differential pair at high frequency. Based on this uncertainty model, a necessary and sufficient condition for robust stability of above electronic circuits at high frequency is presented. This condition guarantees internal stability of the circuit at high frequency with respect to the uncertainty.     

Ultrafast recovery time in a strained InGaAs-AlAs p-i-n modulator

We have performed sub-picosecond resolution measurements of the optical recovery of InGaAs-AlAs multiple quantum well p-i-n structures that exhibit strong excitonic features, a clear quantum confined Stark effect and low photocurrent. The recovery times, measured as a function of applied electrical bias and optical excitation density, are much shorter than that predicted by carrier thermionic emission rates from the quantum wells. An observed ultrafast recovery time of 28 ps makes this material system promising as a fast modulator with low thermal dissipation or as a saturable absorber for semiconductor and fiber laser mode locking     

Analytical Stability Condition of the Latency Insertion Method for Nonuniform GLC Circuits

The latency insertion method (LIM) is a transient simulation technique for circuits and is based on a finite-difference formulation, like the well-known finite-difference time-domain (FDTD) method for solving Maxwells equations. The LIM, like the FDTD method, is only conditionally stable resulting in an upper bound for the time step of the transient simulation. This bound on the time step is a function of the circuit topology and the circuit element values. It is critical to know this bound analytically for a given circuit. However, stability conditions of the LIM have been proven only for 1-D, infinitelylong, distributed uniform RLC circuits, employed in transmission line modeling. For nonuniform circuits, these conditions have been predicted and have been observed experimentally as well but have not been possible to prove using the existing stability analysis techniques. Recently, analytical stability conditions of the LIM for nonuniform RLC circuits have been proven using the Lyapunovs direct method (LDM). However, when a conductance to ground (G) is added to a node of an LC or RLC circuit, the stability conditions cannot be derived using the Lyapunov function proposed. In this brief, analytical stability condition of the LIM is derived for the first time for nonuniform GLC circuits using the LDM with a new Lyapunov function.      

基于RT器件的三值与非门、或非门电路设计

共振隧穿（resonant tunnel,RT）器件本身所具有的微分负阻（negative differential resistance,NDR）特性使其成为天然的多值器件，文中利用RT器件的负阻特性,以开关序列原理为指导,设计了基于RT电路的开关模型,实现了更为简单的三值RT与非门和或非门电路,并利用MOS网络模型,通过SPICE软件仿真验证了所设计电路的正确性，该设计思想可推广到更高值的多值电路设计中。     

Differential BiCMOS logic circuits: fault characterization anddesign-for-testability

Merged Current Switch Logic (MCSL) and Differential Cascode Voltage Switch Logic (DCVSL) are two common structures for differential BiCMOS logic family, that have several potential applications in high-speed VLSI circuits. This paper studies the fault characterization of these BiCMOS circuits. The impact of each possible single defect on the behavior of the circuits is analyzed by simulation. A new class of faults which is unique to differential circuits is identified and its testability is assessed. We propose a design-for-testability method that facilitates testing of this class of faults. Two different realizations for this method are introduced. The impact of this circuit modification on the behavior of the circuit in normal mode is investigated     

An effective parameter extraction method based on memetic differential evolution algorithm

This paper provides an effective method for parameter extraction of microelectronic devices and elements. A novel method, memetic differential evolution (MDE) algorithm, is proposed in this paper. By combining differential evolution (DE) algorithm, mutations in immune algorithm (IA), and special operators for parameter extraction, MDE possesses characteristics of high accuracy, stability, generality, and efficiency. The effectiveness of the method has been shown by two typical examples, including small-signal equivalent circuit models for an AlGaN/GaN HEMT device up to 40 GHz, as well as an equivalent circuit model for on-chip differential spiral inductors. In both cases, the initial values and parameter ranges of the elements in the equivalent circuits are hard to determine in optimization. The results and comparisons with Levenberg-Marquardt (LM) algorithm, genetic algorithm (GA), particle swarm optimization (PSO) algorithm and canonical DE algorithm, demonstrate the superiority of MDE in terms of accuracy and generality.     

Carrier thermalization by phonon absorption in quantum-wellmodulators and detectors

In quantum-confined Stark effect based modulators and quantum-well detectors, carriers are produced at the band-edge by optical absorption. In most applications these earners generate photocurrent and to do so these initially “cold” electrons must thermalize since the photocurrent is dominated by over the barrier escapes of the carriers. The intrinsic speed of the device is thus limited by this thermalization time. We carry out a Monte Carlo simulation to study the carrier heating by phonon absorption in quantum-well structures as a function of well size and barrier height. Carrier thermalization times are dominated by intrasubband polar optical phonon processes and typical times are 1-4 ps depending upon the well and barrier design     

Macromodeling of nonlinear transistor-level receiver circuits

In this paper, a modeling methodology for macromodeling transistor-level receiver circuits has been presented. A few receiver modeling techniques have been proposed in the past, but these modeling techniques only address the loading effect of the receiver circuits, i.e., the input characteristics of the receivers. In this paper, a modeling methodology that addresses both the loading effect as well as the output characteristics of the receiver has been proposed. This modeling technique is simple, accurate, and has huge computational speed-up over transistor-level receiver circuits. To model the input characteristics of the receiver, spline function with finite time difference (SFWFTD) and recurrent neural network (RNN) modeling methods have been used. The output characteristics of the receiver are modeled using a combination of receiver static characteristics and a delay element that takes into account the timing delay of the receiver. The accuracy of the modeling approach has been tested on some test cases and results show good accuracy and substantial speed-up compare to transistor-level receiver circuits. The proposed modeling technique has been extended to multiple ports to estimate sensitive effects like simultaneous switching noise (SSN) when multiple receivers are switching.     

Multiple quantum-well technology takes SEED

Progress in the development of self-electrooptic-effect devices (SEEDs) is discussed. The devices include the resistor-SEED (R-SEED) device, which can be viewed as a simple NOR gate. The symmetric SEED (S-SEED) and the logic-SEED (L-SEED) devices with improved features, functionality, and performance are also considered. The integration of FETs with multiple quantum well (MQW) modulators (FET-SEED), enables optical interconnections of electronic circuits. Where the SEED technology can be used is discussed, and an experimental optical switching fabric made using these devices is described     

An Efficient Way to Assemble ZnS Nanobelts as Ultraviolet‐Light Sensors with Enhanced Photocurrent and Stability

Although there has been significant progress in the fabrication and performance optimization of one‐dimensional nanostructure‐based photodetectors, it is still a challenge to develop an effective and low‐cost device with high performance characteristics, such as a high photocurrent/dark‐current ratio, photocurrent stability, and fast time response. Herein an efficient and low‐cost method to achieve high‐performance ‘visible‐blind’ microscale ZnS nanobelt‐based ultraviolet (UV)‐light sensors without using a lithography technique, by increasing the nanobelt surface areas exposed to light, is reported. The devices exhibit about 750 times enhancement of a photocurrent compared with individual nanobelt‐based sensors and an ultrafast time response. The photocurrent stability and time response to UV‐light do not change significantly when a channel distance is altered from 2 to 100 µm or the sensor environment changes from air to vacuum and different measurement temperatures (60 and 150 °C). The photoelectrical behaviors can be recovered well after returning the measurement conditions to air and room temperature again. The low cost and high performance of the resultant ZnS nanobelt photodetectors guarantee their highest potential for visible‐blind UV‐light sensors working in the UV‐A band.     

阈算术代数系统及多值电流型CMOS电路设计

该文根据电流信号易于实现算术运算的特点,定义了阈算术运算及非负运算,建立了一个适合于电流型电路设计的阈算术代数系统,并在阈算术代数系统中定义和图为阈算术函数的图形表示。在此基础上,通过三值电流型CMOS电路的设计实例,阐述了运用和图将逻辑函数转化为阈算术函数的电流型CMOS电路设计方法。采用TSMC 0.18m CMOS工艺参数的HSPICE模拟结果表明,所设计的电路具有正确的逻辑功能。阈算术代数系统的提出及和图的运用为电流型电路设计提供了一种新的简单有效的方法。     

基于蓝牙通信的智能张力检测系统设计分析

针对基于蓝牙通信的智能张力检测系统设计,从硬件和软件2方面介绍了系统总体设计,并对其实现中涉及的张力传感装置、调理电路、单片机电路等关键技术进行了详细的分析。张力传感器采用三滚轮法的机械结构,使用差分放大电路,并采用变尺度采样算法以减少采样数据量,提升了系统的执行速度。经过分析测试结果,证明该系统具有良好的稳定性,可以极大地提高分析数据的效率。     

低噪声集成压控振荡器声性能分析

提出了一种低相位噪声时基核心电路的压控振荡器的设计方法。通过对采用由普通差分放大器单元和容性耦差分放大器单元构成的环行振荡器的噪声分析 ，由容性耦合差分放大器单元构成的环行振荡器，因其带通特性和负阻特性而具有较好的噪声能力，可用于对频率稳定度有较高要求的ＶＣＯ等电路中。     

Hybrid Computational Simulation and Study of Terahertz Pulsed Photoconductive Antennas

A photoconductive antenna (PCA) has been numerically investigated in the terahertz (THz) frequency band based on a hybrid simulation method. This hybrid method utilizes an optoelectronic solver, Silvaco TCAD, and a full-wave electromagnetic solver, CST. The optoelectronic solver is used to find the accurate THz photocurrent by considering realistic material parameters. Performance of photoconductive antennas and temporal behavior of the excited photocurrent for various active region geometries such as bare-gap electrode, interdigitated electrodes, and tip-to-tip rectangular electrodes are investigated. Moreover, investigations have been done on the center of the laser illumination on the substrate, substrate carrier lifetime, and diffusion photocurrent associated with the carriers temperature, to achieve efficient and accurate photocurrent. Finally, using the full-wave electromagnetic solver and the calculated photocurrent obtained from the optoelectronic solver, electromagnetic radiation of the antenna and its associated detected THz signal are calculated and compared with a measurement reference for verification.     

A method for automatically finding multiple operating points in nonlinear circuits

A new algorithm based on a SPICE-like simulator that searches for multiple operating points automatically, with no user intervention required, is presented. This algorithm, which exploits the asymmetrical properties of nonlinear mappings that describe multistable circuits, has been implemented into a program which automatically finds multiple (in most cases, all) operating points of a circuit. In addition to finding multiple operating points, this method offers another feature: it is capable of detecting the stability of a particular operating point. Another useful feature of this method is that it allows the user to gauge how close a particular circuit is to possessing multiple operating points. For circuits known to possess multiple operating points, this method allows the user to specify which operating point is encountered first. Unlike other continuation methods, circuit element models are not modified; only augmenting resistors are required. Hence, this approach lends itself well as an "add-on" to existing circuit simulators. A number of circuit examples are given.     

Symbolic Steady-State Analysis for Strongly Nonlinear Circuits and Systems

A symbolic method for steady-state analysis of nonlinear circuits and systems is presented. This method is based on the principle of the Equivalent Small Parameter method (the ESP method), which is an improved perturbation technique combined with the harmonic balance method. Using this method, a set of high-order nonlinear differential equations can be solved and the symbolic expressions of the steady-state periodic solutions for the required variables can be obtained. Two examples are given and show that the method is general and can be used for both weakly and strongly nonlinear circuits, and time-variant nonlinear circuits such as switching mode circuits.     

Lapunov’s functions usage in radio circuits’ theory

When analyzing linear differential equations’ stability using Lapunov’s second method, Lapunov’s functions are usually chosen in quadratic form. In radio circuits’ theory Lapunov’s second method by force of existing traditions is applied in rarer cases than for example in mechanics or astronomy. In this article several modifications of the Lapunov’s function are suggested on parametric circuit example. Method which is used here applies to linear radio circuits of general type.     

A problem of stability of parametrical system of two coupled circuits with external conductive connection

Stability provision problem is very important in radio electronics. Each unstable amplifier self-excites and causes damage to radio equipment. Unstability of parametrical oscillating circuits is specified by physical nature of their functioning. Self-exciting appears where temporal variable reactance is present. Two coupled circuits are widely spread in practice. The simplest ones are systems with conductive connection, but nevertheless they are more complicated than parametric oscillating circuit. In this paper a problem of such system stability provision is considered. Analysis is carried out based on Lyapunov’s stability theory.     

单电子晶体管特性的简化分析及其应用

文章在研究单电子晶体管(Single Electron Transistor，SET)I-V特性的基础上，阐明了一种简化分析方法，并据此设计了一个SET积分器，说明了SET积分器的工作条件、结构、性能、参数和特点。仿真结果表明：该积分器的传输特性与采用其它两种方法描述SETI-V特性所构成的积分器传输特性有着良好的一致性。这种简化分析方法同样适用于SET在其它功能电路中的应用。