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A non-quasi-static compact model well suited for the simulation of the electrical behavior of printed organic thin-film transistors (OTFTs) is proposed and validated. The model is based on the discretization of the current continuity equation by using a spline collocation approach while the electrical transport in the organic semiconductor is described by the variable range hopping theory. The model accounts for the presence of parasitic regions that are often found in the layouts of printed OTFTs due to large process tolerances. The model has been implemented in the Verilog-A language and has been validated by a comparison with the capacitance vs. voltage (small signal) characteristics of the devices and measurements made on OTFT-based common-source amplifiers (large signal). A comparison with a quasi-static version of the model is reported.

Large signal stability means that a system can be a transition to a new stable state without losing synchronism after a large disturbance. The large signal stability problem brought by large capacity electrical loads in ac/dc independent power system is prominent, which seriously affects the dynamic security of the system. In view of modeling characteristics of ac/dc system, a generalized state space average large signal modeling method for the ac/dc independent power system in dq-coordinates is proposed. A large signal model of the ac/dc independent power system is constructed, which includes generators, inverter units, rectifying units, and dc/dc converters. The simulation results indicate that the large signal model constructed in this paper can accurately reflect the dynamic characteristics of the system under large disturbances, such as startup and sudden change in load, which is helpful to understand and improve the dynamic performance of the system under large disturbance. Furthermore, with feasibility and effectiveness, the large signal model provides convenience and possibility for the theoretical analysis of large signal stability of ac/dc independent power systems in the future.

A large signal analysis method based on Gummel‐Poon model is proposed to predict nonlinear behavior of InGaP/GaAs HBT. A 2 × 20 μm2 transistor is fabricated with InGaP/GaAs HBT technology. The large signal transconductance Gm, conductance Gbe, and capacitance CBE, CBC are calculated based on the proposed method and measured using a RF testing probe. The calculated and measured results show good consistency up to nonlinear power level. The proposed method is applied to analyze variations of nonlinear large signal intrinsic elements of this transistor with increasing power under different bias conditions, in order to raise benefit of nonlinear consideration for power amplifiers. [ABSTRACT FROM AUTHOR]

A combined supply-inverted bipolar pulser and a Tx/Rx switch is proposed to drive capacitive micromachined ultrasonic transducers (CMUTs). The supply-inverted bipolar pulser adopts a bootstrap circuit combined with stacked transistors, which guarantees high voltage (HV) operation above the process limit without lowering device reliability. This circuit generates an output signal with a peak-to-peak voltage that is almost twice the supply level. It generates a bipolar pulse with only positive supply voltages. The Tx/Rx switch adopts a diode-bridge structure with the protection scheme dedicated to this proposed pulser. A proof- of-concept ASIC prototype has been implemented in 0.18- $\mu \text{m}$ HV CMOS/DMOS technology with 60 V devices. Measurement results show that the proposed pulser can safely generate a bipolar pulse of −34.6 to 45 V, from a single 45 V supply voltage. The Tx/Rx switch blocks the HV bipolar pulse, resulting in less than 1.6 V at the input of the receiver. Acoustic measurements are performed connecting the pulser to CMUTs with 2 pF capacitance and 8 MHz center frequency. The variation of acoustic output pressures for different pulse shapes were simulated with the large signal CMUT model and compared with the experimental results for transmit pressure optimization. A potential implementation of the methods using MEMS fabrication methods is also described. [ABSTRACT FROM AUTHOR]

A second-order accurate finite-difference time-domain (FDTD) model is, for the first time, proposed for efficient and reliable modeling of depletion-mode traveling-wave silicon photonics (SiP) modulators. After reviewing small signal and first-order large signal models for SiP modulators, we derive the second-order FDTD large-signal model for the staggered voltage and current fields in the p-n (PN) loaded transmission line with a series push–pull (SPP) circuit configuration. By modeling the non-even splitting distributive RF voltages on the two PNs, accurate propagation parameters of the two arms of a Mach–Zehnder interferometer (MZI) can be obtained to simulate modulated optical signals. The large signal simulations of 16-QAM SiP modulator at 64 Gbaud are used to demonstrate the application of the developed FDTD model. [ABSTRACT FROM AUTHOR]

Four-leg voltage source inverter is an evolution of the three-leg inverter, and was ought about by the need to handle the non-linear and unbalanced loads. In this work Matlab/ Simulink model is presented using space vector modulation technique. Simulation results for worst conditions of unbalanced linear and non-linear loads are obtained. Observation for the continuity of the fundamental inverter output voltages vector in stationary coordinate is detected for better performance. Matlab programs are executed in block functions to perform switching vector selection and space vector switching.

In this paper, two control strategies for voltage balancing in a modular serial parallel resonant converter modulator system, which is used in a high-voltage-pulsed power application, are presented and verified by simulations and measurements. The system is based on two series parallel resonant converter modules, forming an input series output parallel stack. To obtain the given output voltage pulse of 115 kV, nine of these input series output parallel stacks are connected in parallel at the input and in series at the output, forming an input parallel output series system. A robust input voltage balancing by an auxiliary circuit and an output voltage balancing by control is introduced and proven by measurements. In addition, an alternative approach, where the input and output voltage balancing is achieved purely by control, is given and verified by simulations. For designing the control of this system, a large and a small signal model is derived and the influence of component tolerances is investigated. [ABSTRACT FROM AUTHOR]

This paper presents a physical-based high-frequency nonlinear model of graphene resonant channel transistors (G-RCTs), including a nonlinear electromechanical model of doubled clamped graphene mechanical resonators. To accurately describe the temperature-dependent modal dispersion, both bias- and temperature-dependent effects are considered. The temperature-dependent built-in strain, the bias-based electrostatic force, and the spring restoring force, including the nonlinear term upon deformation, are used to describe the mechanical motion of the suspended beam. The nonlinear model is validated by the measured results of G-RCTs, which indicate that our model can predict the experimental results well. Moreover, the nonlinear effects, including harmonic distortion, third-order intermodulation distortion, and the hysteresis and nonlinear behavior of G-RCTs, are also studied. The results show that the nonlinear physical model can predict the response of G-RCTs very well. These results also show that the mechanical nonlinearity has strong effects on nonlinear distortion for G-RCTs. The nonlinear equivalent circuit model could be useful for nanoelectromechanical system in the applications of high-frequency integrated circuits. [ABSTRACT FROM PUBLISHER]

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Silicon photonic modulators have strong nonlinear behavior in phase modulation and frequency response, which needs to be carefully addressed when they are used in high-capacity transmission systems. We demonstrate a comprehensive model for depletion-mode Mach–Zehnder modulators (MZMs) on silicon-on-insulator, which provides a bridge between device design and system performance optimization. Our methodology involves physical models of p–n–junction phase-shifters and traveling-wave electrodes, as well as circuit models for the dynamic microwave-light interactions and time-domain analysis. Critical aspects in the transmission line design for high-frequency operation are numerically studied for a case of p–n–junction loaded coplanar-strip electrode. The dynamic interaction between light and microwave is simulated using a distributed circuit model solved by the finite-difference time-domain method, allowing for accurate prediction of both small-signal and large-signal responses. The validity of the model is confirmed by the comparison with experimental results for a series push–pull MZM with a 6 mm phase shifter. The simulation shows excellent agreement with experiment for high-speed operation up to 46 Gb/s. We show that this time-domain model can well predict the impact of the nonlinear behavior on the large-signal response, in contrast to the poor prediction from linear models in the frequency domain. [ABSTRACT FROM PUBLISHER]

Accurate modeling of electrothermal effects of GaN electronic devices is critical for reliability design and assessment. In this paper, an electrothermal model for large signal equivalent circuit modeling of AlGaN/GaN HEMTs including self-heating and ambient temperature effects is presented. To accurately describe the effect of ambient temperature, two separate electrothermal networks (Idiss, Rdiss, and Cdiss for self-heating, and Iamb, Ramb, and Camb for ambient temperature effect) are used to describe drain-source current slump due to self-heating and ambient temperature effects, respectively. A temperature-dependent thermal resistance and thermal capacitance model is proposed and implemented in the electrothermal network. The extraction of the thermal parameters is fulfilled by using numerical finite-element method. Single tone on wafer load-pull measurements at two operating frequencies (3 and 14 GHz) are carried out for verification purposes. The results show that good agreements on fundamental output power, the second and third harmonics output power, and power added efficiency have been achieved between simulations and measurements over a wide range of -55 °C to 175 °C. [ABSTRACT FROM AUTHOR]

Four-leg voltage source inverter is an evolution of the three-leg inverter, and was ought about by the need to handle the non-linear and unbalanced loads. In this work Matlab/Simulink model is presented using space vector modulation technique. Simulation results for worst conditions of unbalanced linear and non-linear loads are obtained. Observation for the continuity of the fundamental inverter output voltages vector in stationary coordinate is detected for better performance. Matlab programs are executed in block functions to perform switching vector selection and space vector switching. [ABSTRACT FROM AUTHOR]

This paper presents a fixed frequency operating sliding mode (SM) current control method with fast response and improved stability. Different from the conventional SM control with variable switching frequency, the fixed-frequency SM controller is proposed to control the modulation index and shoot-through duty ratio of the voltage-fed quasi-Z-source inverter (qZSI), which will not increase the passive components and filter design difficulty. A large-signal dynamic model of the system has been established, which can be used for the system stability control in a wide operating range. By using linear approximation, the system small-signal model is also obtained to analyze the control system stability and transient response. Compared with the conventional current mode controller, the proposed SM controller can achieve faster response, lower current ripple and better stability for qZSI when the supply and load variation is large. Experimental results are presented to demonstrate the validity of the theoretical design and the effectiveness of the proposed controller. [ABSTRACT FROM PUBLISHER]

Abstract: This paper presents an improved InGaP/GaAs heterojunction bipolar transistor (HBT) model based on the Vertical Bipolar Inter-Company (VBIC) model. New transport current expression is proposed by considering the heterojunction effect. Collector capacitance is developed due to the mobile charge modulation, and the transit time formula is improved to account for electron velocity variation with the collector field under high current. The extraction flow is demonstrated. The new model has been verified by measurements on I–V, S-parameter, cut-off frequency and large-signal conditions. [Copyright &y& Elsevier]

A scalable active compensatory sub-circuit that focuses on and improves the accuracy of the GaN HEMT large signal model is proposed in this letter. Zero error between the simulated and measured dc $I$– $V$ curves is obtained. Combining empirical and table-based models, time-consuming procedures for parameters extraction and optimizing can be simplified. With a normalizing factor introduced, the scaling of the model is accomplished. The validity of the proposed model is investigated experimentally. This model can be applied for devices with different designs and technology. [ABSTRACT FROM PUBLISHER]

This paper reports the optical control of microwave and millimeter-wave active integrated antennas in which MESFETs are used as the optical control elements. Two types of circuits have been fabricated in which the change of the reactance by the photovoltaic effect of the FET is used. In one of them, the MESFET is used as a passive element which controls the electrical length of the slot antenna by means of the reactance change by optical illumination. It was confirmed that the resonant frequency of this antenna changes by 100 MHz in the X band. In the other circuit, the MESFET used in the oscillator for the active integrated antenna is illuminated optically. An optical tuning range of 63 MHz was observed in the X band. Further, for the latter circuit, a MESFET large signal model was used and the change of the operating frequency was investigated under an assumption of the changes due to optical illumination in the equivalent circuit parameter. It was found that the total of the shifts near the operating frequency of 10 GHz was about 60 MHz if the gate-source capacitance and the drain-gate capacitance are increased by 10 percent. Hence, these parameters have an important role in the optical control. In addition, an FET structure to obtain a larger optical control range has been studied. [ABSTRACT FROM AUTHOR]

A Large-signal model for GaAs FET is derived based on its small-signal S parameters and DC characteristics. The harmonic balance algorithm is applied to analyze and optimize the FET fundamental and harmonic oscillators, and the values of steady current are obtained. In the solving process, a simplified CAD approach is used to obtain the parameters of matching network when the output power is maximum. Finally, a fundamental oscillator and a harmonic oscillator of Q-band are fabricated. The measurements show that the theoretical analysis and experimental results are in good agreement. [ABSTRACT FROM AUTHOR]

In this letter, we present a new large signal model for GaAs metal-semiconductor field effect transistors, incorporating features for enhancing the bias range for which accuracy is maintained, for use in the simulation of microwave circuits. The model parameters for a specific case were extracted from a wide range of dc I-V and S-parameter data, and the simulated behavior was observed to match the measured data closely. The model includes the possibility of showing negative slopes of the I-V curves at high power without sacrificing accuracy in predicting radio frequency behavior, while remaining simple enough for use in simulation tools [ABSTRACT FROM PUBLISHER]

The nonlinear sources of switch‐HEMTs have been well analyzed by using the measured data. The small signal intrinsic capacitances (under both positive and negative Vds operation) have been extracted by an extended small signal model. one‐dimension capacitance model has been effectively applied to model the small signal incremental capacitances directly extracted from the key operation region, which has also automatically taken into account the surface trapping effects. A new capacitance model has been effectively proposed to well fit the key nonlinear source (the deep subthreshold capacitance) of switch‐HEMTs. Simple switching function and additional voltage dependence have been applied to model the wide linear‐region (from high‐Vgs region to deep subthreshold region) of channel current. On/off state small signal insertion loss, small signal isolation, weak harmonics, and power carrying capabilities are accurately predicted by the large signal model. The model shows very good convergence of circuit simulation. Meanwhile, the simple equations and distinguishing among the capacitances accurately make the scaling rules simple and accurate. [ABSTRACT FROM AUTHOR]