Large-signal Behavior Research Articles

Investigation of the large-signal electromechanical behavior of ferroelectric HfO2–CeO2 thin films prepared by chemical solution deposition

Investigation of the large-signal electromechanical behavior of ferroelectric HfO2–CeO2 thin films prepared by chemical solution deposition

Wideband SiGe-HBT Low-Noise Amplifier with Resistive Feedback and Shunt Peaking.

In this work, the design of a wideband low-noise amplifier (LNA) using a resistive feedback network is proposed for potential multi-band sensing, communication, and radar applications. For achieving wide operational bandwidth and flat in-band characteristics simultaneously, the proposed LNA employs a variety of circuit design techniques, including a voltage-current (shunt-shunt) negative feedback configuration, inductive emitter degeneration, a main branch with an added cascode stage, and the shunt-peaking technique. The use of a feedback network and emitter degeneration provides broadened transfer characteristics for multi-octave coverage and a real impedance for input matching, respectively. In addition, the cascode stage pushes the band-limiting low-frequency pole, due to the Miller capacitance, to a higher frequency. Lastly, the shunt-peaking approach is optimized for the compensation of a gain reduction at higher frequency bands. The wideband LNA proposed in this study is fabricated using a commercial 0.13 μm silicon-germanium (SiGe) BiCMOS process, employing SiGe heterojunction bipolar transistors (HBTs) as the circuit's core active elements in the main branch. The measurement results show an operational bandwidth of 2.0-29.2 GHz, a noise figure of 4.16 dB (below 26.5 GHz, which was the measurement limit), and a total power consumption of 23.1 mW under a supply voltage of 3.3 V. Regarding the nonlinearity associated with large-signal behavior, the proposed LNA exhibits an input 1-dB compression (IP1dB) point of -5.42 dBm at 12 GHz. These performance numbers confirm the strong viability of the proposed approach in comparison with other state-of-the-art designs.

Large-signal behavior modeling of GaN HEMTs using SSA augmented ELM algorithm

Large-signal behavior modeling of GaN HEMTs using SSA augmented ELM algorithm

(Invited) III-V Integration on Silicon for Resource-Efficient Sensor-Technology

This work covers integration of advanced III-V semiconductors on silicon substrate for RF-sensor integration up to very high frequencies of 300 GHz and 670 GHz, respectively, including improved active device performance through intelligent engineering of the co-integrated buffer layers. Several Terahertz Monolithically-Integrated Circuits are presented, which demonstrate good gain performance, low-noise, and improve large-signal behavior through the application of the back-gate.

Analysis of Trapping Effect on Large-Signal Characteristics of GaN HEMTs Using X-Parameters and UV Illumination.

GaN high-electron-mobility transistors (HEMTs) have attracted widespread attention for high-power microwave applications, owing to their superior properties. However, the charge trapping effect has limitations to its performance. To study the trapping effect on the device large-signal behavior, AlGaN/GaN HEMTs and metal-insulator-semiconductor HEMTs (MIS-HEMTs) were characterized through X-parameter measurements under ultraviolet (UV) illumination. For HEMTs without passivation, the magnitude of the large-signal output wave (X21FB) and small-signal forward gain (X2111S) at fundamental frequency increased, whereas the large-signal second harmonic output wave (X22FB) decreased when the device was exposed to UV light, resulting from the photoconductive effect and suppression of buffer-related trapping. For MIS-HEMTs with SiN passivation, much higher X21FB and X2111S have been obtained compared with HEMTs. It suggests that better RF power performance can be achieved by removing the surface state. Moreover, the X-parameters of the MIS-HEMT are less dependent on UV light, since the light-induced performance enhancement is offset by excess traps in the SiN layer excited by UV light. The radio frequency (RF) power parameters and signal waveforms were further obtained based on the X-parameter model. The variation of RF current gain and distortion with light was consistent with the measurement results of X-parameters. Therefore, the trap number in the AlGaN surface, GaN buffer, and SiN layer must be minimized for a good large-signal performance of AlGaN/GaN transistors.

Closed-Form Implicit Models for Efficient Simulation of Power Electronics

This document describes novel closed-form implicit (CF-implicit) models of switched-mode power converters, which feature implicit integration but require no iterative numerical solving algorithm for evaluation because they are explicitly solved in CF prior to model execution. The derived models capture the large-signal dynamic behavior of the power converters, so their use and accuracy are not limited to any one set of operating conditions. These models can be directly implemented in any computational environment, including directly on an existing embedded controller. Since no iterative solver is required, the models are highly computationally efficient and have a very predictable worst case execution time (WCET), which makes them especially suitable for real-time (RT) modeling applications, such as hardware-in-the-loop (HIL) simulation or digital twins (DTs). The model derivation process is demonstrated by example on a two-stage power converter, and computational expense is analyzed. A discussion of model error is also included.

Nonlinear dielectric properties of polyimide in high AC electric field

The nonlinear dielectric properties of polyimide (PI) films, excited by high-intensity, AC electric fields, have been measured. This work highlights that nonlinear DC conduction is a component of the AC conductivity and dielectric loss response when surpassing a certain threshold field strength. An additional Poole–Frenkel polarization, induced by high-intensity, high-frequency fields, also contributes to the nonlinearity. This increases the dielectric losses through a charge de-trapping process, the so-called “jacking-up” effect. A novel expression that captures the large signal behavior of the complex permittivity is introduced using the Cole–Cole format. Finally, it is shown that the dielectric properties and power dissipation density in PI films remain fully linear and frequency-independent up to an AC electric field of EPF ∼100 Vrms/μm and more conservatively below a threshold field of EX ∼ 45 V/μm (i.e., end of the ohmic region). Consequently, polyimide-based insulated electronic devices that are designed to continuously operate below this threshold field (including both uniform and fringe fields) will remain immune to a frequency-dependent electrical aging. Their lifetime should not be affected in any way.

Superior mm-Wave Large Signal Power Amplifier Reliability of p-Type FET in a 45-nm Partially-Depleted Silicon-On-Insulator RF Technology

In this letter, we have explored the DC, small and large-signal RF reliability of the Power Amplifier (PA) cell for mm-wave applications under DC and RF stress. The PA cell comprises of a single transistor that employs 45RFSOI technology. For the first time here, a PA cell consisting of p-channel partially depleted Silicon-On-Insulator (PD-SOI) FET has been investigated for large-signal reliability behavior. At the same stress conditions, the impact of hot carrier degradation (HCD) on a p-channel FET (PFET) PA cell is also compared with the n-channel FET (NFET) PA cell. As the reliability of the PFET PA cell is superior than NFETs, a deeper investigation of hot carrier degradation and its impact on PA cell reliability is carried out. The PA cell is subjected to extensive RF characterization for varying DC stress and RF power at the gate terminal. The behavior of the time slope exponent of the PFET PA cell is studied to understand the nature of defects. Accelerated aging experiments using DC bias at drain/gate terminals and RF power at the gate terminal is performed. These results show that the RF reliability of the PFET PA cell is superior than its counterpart NFET PA cell at mm-wave frequencies.

Transient Stability Analysis of Direct Drive Wind Turbine in DC-Link Voltage Control Timescale during Grid Fault

Transient stability during grid fault is experienced differently in modern power systems, especially in wind-turbine-dominated power systems. In this paper, transient behavior and stability issues of a direct drive wind turbine during fault recovery in DC-link voltage control timescale are studied. First, the motion equation model that depicts the phase and amplitude dynamics of internal voltage driven by unbalanced active and reactive power is developed to physically depict transient characteristics of the direct drive wind turbine itself. Considering transient switch control induced by active power climbing, the two-stage model is employed. Based on the motion equation model, transient behavior during fault recovery in a single machine infinite bus system is studied, and the analysis is also divided into two stages: during and after active power climbing. During active power climbing, a novel approximate analytical expression is proposed to clearly reveal the frequency dynamics of the direct drive wind turbine, which is identified as approximate monotonicity at excitation of active power climbing. After active power climbing, large-signal oscillation behavior is concerned. A novel analysis idea combining time-frequency analysis based on Hilbert transform and high order modes is employed to investigate and reveal the nonlinear oscillation, which is characterized by time-varying oscillation frequency and amplitude attenuation ratio. It is found that the nonlinear oscillation and even stability are related closely to the final point during active power climbing. With a large active power climbing rate, the nonlinear oscillation may lose stability. Simulated results based on MATLAB® are also presented to verify the theoretical analysis.

A Time-Domain Multi-Tone Distortion Model for Effective Design of High Power Amplifiers

This paper proposes a new time-domain multi-tone distortion (TD-MTD) model suitable for accurately predicting the non-linear behavior of packaged high power radio frequency (RF) transistors over a range of discrete non-uniformly distributed frequencies. This proposed TD-MTD model uses a single expression rather than multiple distinct frequency specific behavioral models to describe the underlying behavior of the high power RF transistor at multiple fundamental frequencies. Furthermore its extraction is carried out using a time-domain representation of the travelling waves that can be acquired using a generic vector load-pull characterization system and without imposing additional requirements. The proposed model is extracted as an artificial neural network (ANN) and is implemented as a Netlist to serve in a harmonic balance simulator based power amplifier design process. The proposed model is validated in two phases. First, its ability to reproduce the large-signal behavior of a high power RF LDMOS transistor was demonstrated in simulation. Then, the TD-MTD model was used to validate the design of a high power two-way asymmetric Doherty power amplifier and the simulated output-power-dependent power efficiency, AM/AM, AM/PM and input return loss characteristics were compared to those obtained in measurement. The excellent agreement between the simulation and measurement results confirms the usefulness of the proposed model despite the simplicity of its extraction routine and measurement data.

Large-Signal Behavior Modeling of GaN P-HEMT Based on GA-ELM Neural Network

Large-Signal Behavior Modeling of GaN P-HEMT Based on GA-ELM Neural Network

Theoretical Analysis and Experimental Validation of Flying-Capacitor Multilevel Converters Under Short-Circuit Fault Conditions

Addressing the increasing demand for high-efficiency and high-power-density converters, the flying-capacitor multilevel converter has shown itself as a promising topology. A key advantage of this topology is the reduced voltage rating of the switches, though also makes it vulnerable to device failure during short-circuit conditions. Despite large interest in fault-tolerant operation of these converters, alongside detailed descriptions of flying-capacitor balancing, little research has focused on the converter short-circuit fault analysis, which may cause a switch failure if not properly designed for. Therefore, this article presents a comprehensive model describing the large-signal short-circuit switching behavior of a general N-level flying-capacitor multilevel converter. Highly simplified models used to predict the evolution of the switch current and voltage stress during the fault are proposed, targeted at practicing engineers for conservative design guidelines. These models are used to determine the critical time for remedial action of the converter before reaching some predefined maximum conditions. A 2-to-10-level fully configurable flying-capacitor multilevel converter and a fault circuit hardware prototype are used to experimentally perform different short-circuit tests that show a good match to the measured behavior.

An efficient drain-lag model for microwave GaN HEMTs based on ASM-HEMT

AbstractLarge-signal modeling of Gallium Nitride (GaN) based high electron mobility transistors (HEMTs) demands a proper description of trapping effects. In this paper, a new, simplified yet accurate drain-lag description is proposed, enhancing the simulation accuracy and the extraction flow of the physics-based compact model ASM-HEMT. The present study investigates the impact of drain lag on specific physical phenomena, focusing on the relation between trap states, surface-potential calculations, and electron transport properties. It is supplemented with a revised extraction procedure, minimizing the required measurements, thereby the undesired consequences of several passes on the same device, using pulsed I-V and pulsed S-parameters only, and approaches for efficient and accurate simulation results. We show that the proposed trap model is a determinative tool for simulating both small and large-signal behavior predicting precisely S-parameters and load-pull performance.

Neural-Network Based Modeling of I/O Buffer Predriver under Power/Ground Supply Voltage Variations.

This paper presents a neural-network based nonlinear behavioral modelling of I/O buffer that accounts for timing distortion introduced by nonlinear switching behavior of the predriver electrical circuit under power and ground supply voltage (PGSV) variations. Model structure and I/O device characterization along with extraction procedure were described. The last stage of the I/O buffer is modelled as nonlinear current-voltage (I-V) and capacitance voltage (C-V) functions capturing the nonlinear dynamic impedances of the pull-up and pull-down transistors. The mathematical model structure of the predriver was derived from the analysis of the large-signal electrical circuit switching behavior. Accordingly, a generic and surrogate multilayer neural network (NN) structure was considered in this work. Timing series data which reflects the nonlinear switching behavior of the multistage predriver’s circuit PGSV variations, were used to train the NN model. The proposed model was implemented in the time-domain solver and validated against the reference transistor level (TL) model and the state-of-the-art input-output buffer information specification (IBIS) behavioral model under different scenarios. The analysis of jitter was performed using the eye diagrams plotted at different metrics values.

Optimal Controller Design for Transient Stability Enhancement of Grid-Following Converters Under Weak-Grid Conditions

Modeling and design-oriented control of transient stability of grid-following converters have attained an increasing interest in recent years. Despite novel nonlinear models enabling a design-oriented enhanced transient stability controller, the focus has so far been limited to study only the synchronization dynamics of the phase-locked loop. To expand upon the knowledge of the large-signal performance and stability, this article proposes a systematic analysis procedure of a grid-following converter under weak-grid conditions and large-signal disturbances including the outer dc-link and ac-side voltage control loops. A reduced-order large-signal model is used to analyze the large-signal nonlinear behavior of the system using the area of the basin of attraction as a measure for large-signal robustness. Here, stabilizing and destabilizing trends for outer-loop controller parameters are given. Through a surrogate-model expensive black-box optimization algorithm, a computational-efficient optimal design of the outer-loop controller parameters is proposed to maximize the large-signal robustness. Finally, a recommendation and a design guideline for converter constraints and outer-loop controller parameters are given. This can be used to identify the influencing parameters for grid-following converters under large-signal disturbances, and as a tool for fast controller optimization toward large-signal robustness.

A Godunov-Type Stabilization Scheme for Large-Signal Simulations of a THz Nanowire Transistor Based on the Boltzmann Equation

A stabilization method is presented for the Boltzmann equation (BE) that is based on Godunov’s approach applied directly in the phase space. This makes it possible to perform transient simulations under quasiballistic conditions and to include the Pauli principle in the scattering integral without further approximations. The method ensures positive distribution functions by construction. The BE is solved self-consistently together with the Poisson and Schrodinger equations by the Newton–Raphson method for a nanowire silicon nMOSFET, for which the stationary ${I}$ – ${V}$ characteristics, the small-signal admittance parameters, and the switching behavior are calculated. The large-signal behavior of the MOSFET as an amplifier is evaluated by cyclostationary simulations including power gain and the output power at higher harmonics. The current responsivity of the MOSFET operated as a passive mixer is simulated up to terahertz (THz) frequencies including the quasiballistic case with negligible scattering.

Nonlinear Analysis of Cross-Coupled Super-Regenerative Oscillators

In this paper, a nonlinear analysis of cross- coupled super-regenerative oscillators (SROs) is presented. The start-up and decay envelopes of the oscillator output are studied in relation to the input. The SRO start-up time and the maximal achievable quenching frequency are investigated. For phase modulation purposes, the relation between the initial phases of the input and output signals is investigated. In addition, a frequency-domain analysis is performed to ease the characterization of circuit prototypes at frequencies where time-domain measurements are not possible. The analytical results are verified by circuit-level simulations and measurements of a 2.4-GHz SRO. This study provides design guidelines for the design of SROs in cross-coupled architectures and helps in determining the optimal system parameters when targeting both amplitude and phase modulations. To the authors' best knowledge, this is the first study investigating analytically the phase relation between the SRO input and output signals and the nonlinear large-signal behavior of SROs.

Efficient Design Strategy for Optimizing the Settling Time in Three-Stage Amplifiers Including Small- and Large-Signal Behavior

An analytical criterion for the optimization of the small-signal settling time in three-stage amplifiers is carried out. The criterion is based on making equal the two exponential decays of the step response. Including slew-rate effects, a useful design strategy for the design of three-stage operational transconductance amplifier is provided. Extensive time-domain simulations on a transistor-level design in a 65-nm CMOS process confirm the validity of the proposed approach.

Design of Three-Stage OTA Based on Settling-Time Requirements Including Large and Small Signal Behavior

In this paper we are going to analyze the settling-time in single-, two- and three-stage amplifiers with the intent of deriving approximate but useful design equations that include the effects of the zeros and of the slew-rate limitations. The analysis is mainly devoted to the definition of an approach for the design of three-stage CMOS operational transconductance amplifiers from settling-time specifications. A design example is carried out to validate the proposed approach.

Origins of Soft-SwitchingCossLosses in SiC Power MOSFETs and Diodes for Resonant Converter Applications

The recent development and commercialization of wide bandgap (WBG) power semiconductors, specifically gallium nitride (GaN) and silicon carbide (SiC), have driven the increase in switching frequency for soft-switching power converters, such as the Class E, Class Φ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> , and Class DE resonant inverters and rectifiers. However, prior literature has characterized numerous commercial GaN and SiC devices using the Sawyer-Tower circuit and discovered significant large-signal C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> oss</sub> charge-voltage hysteresis. This C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> oss</sub> hysteresis, equivalent to OFF-state energy loss, is highly dependent on the frequency and voltage across the device, hindering the efficiency and performance of MHz-range soft-switched converters. This article is the first to explain the origin of the C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> oss</sub> loss in SiC power devices as charging and discharging conduction losses at the termination of the device. The loss characteristics relative to the operating voltage, frequency, dV/dt, and temperature are dictated by incomplete ionization. Incomplete ionization also highlights a significant inconsistency between the large-signal C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> oss</sub> behavior and small-signal behaviors, which is often the model used in manufacturers' datasheets and SPICE simulations. The large-signal charge-voltage behavior is transient, where the charge in C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> oss</sub> depends on the rate of the voltage swing across the device. We validate these hypotheses through mixed-mode simulations using the Sentaurus technology computer-aided design (TCAD) and experimentally using commercial and custom SiC devices.