Subthreshold analysis of an MOS analog switch

Charge injection error in the presence of subthreshold effects has been analyzed. It is confirmed that the subthreshold effect is significant at low voltage falling rates. A simplified model is derived using an appropriate approximation. Predictions are compared to the results of a SPICE simulation, a nonquasi-static (NQS) model simulation and experimental results. Excellent agreement between the modified and NQS model and recently published experimental results was obtained. This analytical model is computationally efficient compared to the SPICE and NQS models and provides physical insight into the switching errors     

Determining the onset frequency of nonquasistatic effects of theMOSFET in AC simulation

The frequency dependence of nonquasistatic (NQS) operation in MOS transistors is studied. With the help of a two-dimensional device simulator, a time varying sine function is applied to the gate at different frequencies. The inversion channel charge variation in response to the input signal at high frequency is compared with that at dc. By observing the frequency that generates an observable delay in channel charge response to the applied signal, the onset frequency of the NQS effect can be determined, which gives a limit to the valid quasistatic (QS) assumption. It was found that the onset frequency of the NQS effect is very close to f_T, the unity gain frequency of a transistor, and the QS approximation is sufficient for most of the practical applications     

SiGe HBT非准静态小信号等效电路的参数提取

提出了一种硅锗异质结双极型晶体管（SiGe HBT）非准静态效应的小信号等效电路模型的参数提取方法。整个参数提取过程建立在由非准态效应的小信号等效电路推导出的一系列泰勒级数解析公式并结合参数直接法,该方法依赖于测量的S参数,不使用任何的数值优化法,参数提取结果使用CAD仿真验证。结果表明该参数提取方法简单易行,较为精确,该方法能够用到不同工艺SiGe HBT参数提取。     

A new approach to model nonquasi-static (NQS) effects for MOSFETs. Part II: Small-signal analysis

We present a new approach to model nonquasi-static (NQS) effects in a MOSFET in a small-signal situation. The model derived here is based on the large-signal NQS model previously proposed. The derivation of the small-signal model is presented. The small-signal parameters obtained with this model prove to be accurate up to very high frequencies. An excellent match between the new model and device simulation results has been observed even when the frequency is many times larger than the cutoff frequency.     

A robust and physical BSIM3 non-quasi-static transient and ACsmall-signal model for circuit simulation

A new non-quasi-static (NQS) MOSFET model, which is applicable for both large-signal transient and small-signal ac analysis, has been developed. It employs a physical relaxation time approach to take care of the finite channel charging time to reach equilibrium and the effect of instantaneous channel charge re-distribution. The NQS model is formulated independently from the dc I-V and the charge-capacitor model, thus can be easily applied to any existing simulators. The model has been implemented in the newly released BSIM3 version 3, and comparison has been made among this model, common quasi-static (QS) SPICE models and PISCES two-dimensional (2-D) numerical device simulator. While predicting accurate NQS behavior, the time penalty for using the new model is only about 20-30% more than the common QS models. It is much less than the time required by other NQS models reported. Limitations and compromises between simplicity, efficiency and accuracy are also discussed     

压电超声无线能量传输通道阻抗特性研究

基于压电晶体沿厚度方向振动的数学模型,用等效电路法分析得到表面镀银的某型压电超声换能器的谐振频率和反谐振频率,与实测结果相符。在考虑耦合层影响条件下,建立了由外部压电换能器-金属壁-内部压电换能器所构成超声无线能量传输通道的等效电路模型,并仿真得到了通道的阻抗特性,与高精度阻抗分析仪实际测得的阻抗进行比较,验证了所建模型的准确性。     

Frequency-dependent resistive and capacitive components in RFMOSFETs

It is found from measured high frequency (HF) S-parameter data that the extracted effective gate sheet resistance (R_gsh), effective gate unit-area capacitance (C_{gg, unit}), and transconductance (G_m) in radio-frequency (RF) MOSFETs show strong frequency dependency when the device operates at frequencies higher than some critical frequency. As frequency increases, R_gsh increases but C_{gg, unit} and G_m decrease. This behavior is different from what we have observed at low or medium frequencies, at which these components are constant over a frequency range. This phenomenon has been observed in MOSFETs with L_f longer than 0.35 μm at frequencies higher than 1 GHz, and becomes more serious as L_f becomes longer and the frequency higher. This behavior can be explained by a MOSFET model considering the Non-Quasi-Static (NQS) effect. Simulation results show that an RF model based on BSIM3v3 with the NQS effect describes well the behaviors of both real and imaginary parts of Y₂₁ of the device with strong NQS effect even though its fitting to Y₁₁ needs to be improved further     

High-frequency characterization and modeling of distortion behavior of MOSFETs for RF IC design

High frequency (HF) distortion of MOSFETs has been characterized at different frequencies and bias conditions with a single tone measurement system. The results show that a MOSFET has much higher "low frequency limit" (LFL) than a bipolar transistor with similar critical dimensions, implying that the HF distortion characteristics of MOSFETs operating at a frequency lower than LFL is dictated by its low-frequency behavior. This discovery is useful for designers and modelers to validate the distortion of a MOSFET model for RF application. It has also been found that the second harmonic P/sub f2/ reaches to its minimum as f/sub T/ peaks, due to a similar nonlinearity cancellation as in bipolar transistors. Furthermore, the measured data shows fairly constant distortion characteristics over a wide range of drain biases as the device operates in the saturation region. Simulation with a BSIM3v3-based sub-circuit model demonstrates that the distortion behavior of MOSFETs can be well predicted by an RF model if it can accurately describe both dc and ac characteristics with proper parameter extraction. Sensitivity of the distortion on various physical effects, such as the mobility degradation, velocity saturation, channel length modulation, and drain-induced barrier lowering, are also studied to provide insights of the key nonlinearity variation contributors from a practical modeling point of view.     

Low distortion 1.3 μm strained-layer MQW-DFB laser for AM-SCMtransmission systems with large channel capacity

1.3-μm strained-layer multiquantum-well distributed-feedback (SL-MQW-DFB) lasers with extremely low distortion and low noise characteristics up to high output-power as well as over wide frequency range were successfully fabricated. This was achieved by both the high relaxation oscillation frequency (f_r) characteristics of the laser with the optimized SL-MQW active structure and the suppression of nonradiative current with relatively long laser cavity length. By using the SL-MQW laser with a 400-μm long cavity as a light source for CATV transmission system, high quality AM-SCM transmissions with the largest channel capacity (151 channel) was demonstrated due to low distortion characteristics at high output power. Also, for the laser with 300 μm long cavity, extremely low bias-current operation (17 mA above threshold) is realized in high quality 100 channel AMSCM transmissions, due to high f_r at low bias-current     

内通道轴向风速对强激光相位特性的影响

针对内通道传输过程中激光束相位特性的变化,建立了内通道中光场-流场的耦合仿真模型,通过引入湍流相位屏模拟了内通道中湍流扰动对传输光束波前相位的影响。在此基础上,定量计算了不同轴向风速条件下内通道传输光束的波前相位特性,并结合自适应波前校正模型,分析了激光束经内通道传输后的波前校正效果。研究结果表明,随着轴向风速的增大,激光束波前相位中的高频成分呈现出先增大后减小的趋势,经自适应波前校正后的光束质量也呈现出类似趋势,且当轴向风速约为0.65 m/s时畸变波前中的高频成分最多,经波前校正后的光束质量最差。该模型能够为激光控制系统的设计和性能评估提供一定参考。     

Non-quasi-static effects in advanced high-speed bipolar circuits

A detailed study on the non-quasi-state (NQS) effects in advanced high-speed bipolar circuits is presented. An NQS Gummel-Poon-compatible lumped circuit model, which accounts for carrier propagation delays across various quasi-neutral regions in bipolar devices, is implemented in the ASTAP circuit simulator. The effects are then evaluated and compared with those for the conventional Gummel-Poon model for the emitter-coupled logic (ECL) circuit, the non-threshold-logic (NTL) circuit, and various advanced circuits utilizing active-pull-down schemes. For the ECL circuit, the effect decreases with reduced power level and increased loading. For the NTL circuit, due to its front-end configuration, the effect is more significant than that for the ECL circuit but tends to increase with reduced power level. As the passive resistors (and the associated parasitic RC effect) are decoupled from the delay path and the circuit delay is made more intimately related to the intrinsic speed of the devices in various advanced active-pull-down circuits, the delay degradation due to NQS effect becomes more significant     

Investigation of very fast and high-current transients in digitalbipolar IC's using both a new compact model and a device simulator

The design and optimization of high-speed integrated bipolar circuits requires accurate and physical transistor models. For this, an improved version of the compact model HICUM was developed. It is an extension of the small-signal model recently described to the large-signal (transient) case. The model, which takes into account emitter periphery and non-quasi-static (NQS) effects, is semi-physical, allowing the calculation of its elements for arbitrary transistor geometries from specific electrical and technological data. This is an important precondition for transistor optimization in a circuit and for worst case analysis. The model was verified for basic building blocks of high-speed digital circuits like emitter follower and current switch. For this, mixed-mode device/circuit simulation is used instead of measurements, since the latter would give too large errors for the fast transients of interest. It is demonstrated that-in contrast to the obsolete but frequently used SPICE Gummel/Poon model-the new HICUM is well suited for modeling very-high-speed transistor operation also at high current densities. Moreover, it is shown that at very fast transients the influence of NQS effects can no longer be neglected. As a practical application example, a high-speed E²CL circuit is simulated using the new model. The results show again that high-current models are very useful for designing IC's at maximum operating speed. This is because the optimum emitter size is often the minimum size, which is limited by high-current effects. Especially, in the case of current spikes (e.g., in emitter followers) it is difficult to find the optimum emitter size without having adequate transistor models     

An improved deep submicrometer MOSFET RF nonlinear model with newbreakdown current model and drain-to-substrate nonlinear coupling

An improved deep submicrometer (0.25 μm) MOSFET radio-frequency (RF) large signal model that incorporates a new breakdown current model and drain-to-substrate nonlinear coupling was developed and investigated using various experiments. An accurate breakdown model is required for deep submicrometer MOSFETs due to their relatively low breakdown voltage. For the first time, this RF nonlinear model incorporates the breakdown voltage turnover trend into a continuously differentiable channel current model and a new nonlinear coupling circuit between the drain and the lossy substrate. The robustness of the model is verified with measured pulsed I-V, S-parameters, power characteristics, harmonic distortion, and intermodulation distortion levels at different input and output termination conditions, operating biases, and frequencies     

A Unified Nonquasi-Static MOSFET Model for Large-Signal and Small-Signal Simulations

The spline collocation-based nonquasi-static (NQS) model is further developed to include all regions of operation and small-geometry effects. The new formulation provides a unified (hence consistent) approach to both large-signal and small-signal NQS modeling and is sufficiently flexible to work with any surface-potential-based MOSFET model. The model is verified through comparison with the channel segmentation method, two-dimensional numerical simulations, and experimental results and demonstrates a controlled tradeoff between model accuracy and efficiency. The new NQS model has been implemented into PSP model. Circuit simulations are given to demonstrate the accuracy and applicability of the new model.     

Distortion in single-, two- and three-stage amplifiers

Nonlinear distortion in single-, two-, and three-stage operational amplifiers (opamps) is the main scope of this paper. For each opamp, distortion contributions from different groups of transistors are identified and plotted versus frequency. This makes it possible to find the strongest sources of distortion in the various frequency regions. Further, equations that describe the third harmonic as a function of circuit parameters and input frequency are presented. Despite the simplifications, these equations describe the third harmonic accurately. Further, they provide insight and understanding by connecting distortion to circuit parameters such as transconductances, capacitances, poles, and zeros. The comparison of the opamps shows that each opamp has a frequency region where the distortion is lower than for the other two. The three-stage op amp has far lower distortion at low frequencies, the single-stage op amp is better at high frequency and the two-stage op amp is best for the mid frequency range.     

Compact Modeling of Anomalous High-Frequency Behavior of MOSFET's Small-Signal NQS Parameters in Presence of Velocity Saturation

This paper presents a physical charge-based compact small-signal nonquasi-static (NQS) model for MOST, including velocity saturation and valid in all regions of inversion (from weak to strong inversion). This model intrinsically predicts the anomalous high-frequency behavior of transadmittance$(y_ dg)$in saturation, which was observed earlier in both device simulation and measurement. It also shows that the inclusion of velocity saturation causes the magnitude of the gate-to-drain admittance$y_ dg$to start to increase (instead of decreasing) above a certain frequency and its real part also starts to increase in the negative direction instead of becoming zero. In addition, even for a long channel MOST, the weak inversion charge present at the drain can also affect the$y_ dg$in a similar way.     

双信号单通道红外光传输

以FPGA作为控制核心,设计了一种脉冲频率调制(PFM)与脉冲宽度调制(PWM)对信号先后调制,并用红外光来进行同时传输的装置。发送端通过FPGA自带的高速AD对音频信号采样,通过PFM与PWM来实现音频信号的调制,接收端FPGA对光脉冲进行解调输出。设计中发射电路与接收电路完全采用分离元件进行构建,具有成本低、功耗小、传输效率高等优点。通过对设计结果的分析可以得到在12 m内,1～10 kHz的音频信号和数字信号能够在一个通道里进行无失真的实时传输。传输信号经过中继站实现信号向不同方向转发的功能。同时中继站的功耗为0.08 W,满足节能的要求。     

PSpice在高频电子线路中的应用

PSpice软件是目前应用最广的电子线路仿真软件，他可以根据电路的结构和元器件参数对电路进行仿真分析，从而可以方便、精确地判断电路设计的正确性。本文介绍了PSpice软件的功能和特点，利用PSpice对包络检波器进行了仿真，并对包络检波器的两种特有失真（惰性失真和负峰切割失真）进行了观察和分析。通过这一实例较详细地说明如何用PSpice软件对高频电子电路进行仿真与性能分析。从而为高频电子线路的设计和教学提供了一个新的途径。     

Three-Phase Rectifier With Active Current Injection and High Efficiency

An active current injection network for a three-phase rectifier is proposed. The proposed circuit uses three bidirectional switches operating at low frequency and a half-bridge inverter operating at high frequency. It also uses an inductor in order to make the current modulation. Because only 3.7% of the total power delivered to the load is processed by the injection network, the proposed converter offers high efficiency, and not only a high power factor is obtained but also the total harmonic distortion is reduced. Operation, analysis, simulation, and experimental results are shown in this paper.