Large-signal Equivalent Circuit Model Research Articles

Large-Signal Equivalent-Circuit Model of Asymmetric Electrostatic Transducers

This article presents a circuit model that is able to capture the full nonlinear behavior of an asymmetric electrostatic transducer whose dynamics are governed by a single degree of freedom. Effects such as stress-stiffening and pull-in are accounted for. The simulation of a displacement-dependent capacitor and a nonlinear spring is accomplished with arbitrary behavioral sources, which are a standard component of circuit simulators. As an application example, the parameters of the model were fitted to emulate the behavior of an electrostatic MEMS loudspeaker whose finite-element (FEM) simulations and acoustic characterisation where already reported in the literature. The obtained waveforms show good agreement with the amplitude and distortion that was reported both in the transient FEM simulations and in the experimental measurements. This model is also used to predict the performance of this device as a microphone, coupling it to a two-stage charge amplifier. Additional complex behaviors can be introduced to this network model if it is required.

An Extensive Large Signal Equivalent Circuit Model of GaAs-PIN Photodiode

Based on the variation trend of the depletion layer of GaAs-PIN photodiode (PD) under different optical power and reverse bias voltages, an extensive large-signal equivalent circuit model that characterizes PD in non-punch-through and punch-through states is proposed in this article. According to the analysis of the PD’s depletion layer variation, the nonlinear parameters of the model are described by exponential function and Gaussian function. To verify the reliability of equivalent circuit model, on-chip measurements were performed on PIN-PD fabricated by commercial GaAs process, and the measured <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${I}$ </tex-math></inline-formula> - <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${V}$ </tex-math></inline-formula> and reflection coefficient agree with the proposed model simulation results well. Furthermore, using the proposed model for simulation with CAD tools shows that reducing junction capacitance has potential in improving PD output power and gain flatness. At the same time, the model provides a certain reference for selecting bias condition in the design of the PD matching network and fabricating PD with high power output.

An Improved Large-Signal Equivalent Circuit Model for Partially Depleted Silicon-on-Insulator MOSFET

In this article, a nonlinear capacitance model for a large-signal compact model of partially depleted (PD) silicon-on-insulator (SOI) transistors is proposed. When the transistors are operated in the saturation and triode region, the gate-source capacitance ( C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">gs</sub> ) and the gate-drain capacitance ( C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">gd</sub> ) change with the gate-source voltage ( V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">GS</sub> ) nonlinearly. C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">gs</sub> will emerge a significant compression phenomenon in the triode region. This capacitance model adds a hyperbolic tangent function to the conventional model's function to characterize this phenomenon. Besides, the nonlinear drain current model is obtained on the basis of a unified empirical model. To validate this improved large-signal equivalent circuit model, two different transistors are manufactured in a commercial 180-nm body-contact (BC) PD-SOI process. On-wafer measurement is implemented to obtain the experimental data. Then the calculated results of the model are compared with the measurement data. The relative root-mean-square-error (RRMSE) is less than 6.59% for output power, 9.03% for power-added efficiency (PAE), and 2.72% for the gain respectively.

Schottky Diode Large-Signal Equivalent-Circuit Parameters Extraction for High-Efficiency Microwave Rectifying Circuit Design

A novel parameter extraction method for the Schottky diode’s large-signal equivalent-circuit model is proposed, and used to design high-efficiency microwave rectifying circuits. This method extracts the nonlinear SPICE parameters in the equivalent-circuit from measured I-V and C-V data, and the linear parasitic parameters from the broadband small-signal S-parameters. Moreover, it employs a de-embedding technology that adopts an equivalent circuit to remove the influence of the test fixture in the S-parameters measurement, thereby additional TRL calibration kits are not required. As a sample, large-signal equivalent-circuit parameters of the Schottky diode with model number MA4E1317 are extracted by the proposed method. Then it was used to design two Class-F microwave rectifying circuits working at 2.45 GHz and 5.8 GHz, respectively. Owing to the high accuracy of the extracted parameters by the proposed method, the simulation results such as the large-signal transient voltage waveforms across the diode agree well with the measured ones. Furthermore, two rectifying circuits exhibit very high rectifying efficiencies (e.g., 83.5% at 2.45 GHz and 82.1% at 5.8 GHz with 16.8 dBm input power).

A Nonlinear Lumped Equivalent Circuit Model for a Single Uncollapsed Square CMUT Cell.

An accurate nonlinear lumped equivalent circuit model is used for modeling of capacitive micromachined ultrasonic transducers (CMUTs). Finite-element analysis (FEA) is a powerful tool for the analysis of CMUT arrays with a small number of cells while with the harmonic balance (HB) analysis of the lumped equivalent circuit model, the entire behavior of a large-scale arbitrary CMUT array can be modeled in a very short time. Recently, an accurate nonlinear equivalent circuit model for uncollapsed single circular CMUT cells has been developed. However, the need for an accurate large-signal circuit model for CMUT cells with square membranes motivated us to produce a new nonlinear large-signal equivalent circuit model for uncollapsed CMUT cells. In this paper, using analytical calculations and FEA as the tuning tool, a precise large signal equivalent circuit model of square CMUT dynamics was developed and showed excellent agreement with finite-element modeling (FEM) results. Then, different CMUT single cells with square and circular membranes were fabricated using a standard sacrificial release process. Model predictions of resonance frequencies and displacements closely matched experimental vibrometer measurements. The framework presented here may prove valuable for future design and modeling of CMUT arrays with square membranes for ultrasound imaging and therapy applications.

Power Supply- and Temperature-Aware I/O Buffer Model for Signal-Power Integrity Simulation

This paper presents the development and evaluation of a large-signal equivalent circuit model that accounts for the power supply fluctuation and temperature variation of I/O buffers circuit designed based on the fully depleted silicon on insulator (FDSOI) 28 nm process for signal-power integrity (SPI) simulation. A solid electrical analysis based on the working mechanisms of the nominal I/O buffer information specification- (IBIS-) like model is presented to support the derivation of an accurate and computationally efficient behavioral model that captures the essential effects of the power supply bouncing under temperature variation. The formulation and extraction of the Lagrange interpolating polynomial are investigated to extend the nominal equivalent circuit model. The generated behavioral model is implemented using the Newton-Neville’s formula and validated in simultaneous switching output buffers (SSO) scenario under temperature variation. The numerical results show a good prediction accuracy of the time domain voltage and current waveforms as well as the eye diagram of the high-speed communication I/O link while speeding-up the transient simulation compared to the transistor level model.

A compact D-band monolithic APDP-based sub-harmonic mixer

The paper presents a compact D-band monolithic sub-harmonic mixer (SHM) with 3μm planar hyperabrupt schottky-varactor diodes offered by 70nm GaAs mHEMT technology. According to empirical equivalent-circuit models, a wide-band large signal equivalent circuit model of the diode is proposed. Based on the extracted model, the mixer is implemented and optimized with a shunt-mounted anti-parallel diode pair (APDP) to fulfill the sub-harmonic mixing mechanism. Furthermore, a modified asymmetric three-transmission-line coupler is devised to achieve high-level coupling and minimize the chip size. The measured results show that the conversion gain varies between −13.9dB and −17.5dB from 110GHz to 145GHz, with a local oscillator (LO) power level of 14dBm and an intermediate frequency (IF) of 1GHz. The total chip size including probe GSG pads is 0.57×0.68mm2. In conclusion, the mixer exhibits outstanding figure-of-merits.

A Large-Signal Statistical Model and Yield Estimation of GaN HEMTs Based on Response Surface Methodology

A novel nonlinear large-signal equivalent circuit statistical model of GaN HEMTs based on response surface methodology (RSM) is proposed in this letter. Thirty-four GaN HEMTs from 10 batches are measured and all the parameters in the large-signal equivalent circuit model are extracted by an in-house parameters extraction program. We choose the four most sensitive parameters of the drain-source current model and the gate charge model. The statistical method is modeled by using response surface methodology to change the range of the four parameters. The statistical model is implemented in Agilent-ADS and three S-band GaN HEMT power amplifier are designed by using the established statistical model for validation. The results show that good accuracy has been achieved by comparing measured and simulated output power (Pout) and power added efficiency (PAE). This method is simple and accurate for GaN HEMT power amplifier design and yield estimation.

An Improved VBIC Large-Signal Equivalent-Circuit Model for SiGe HBT With an Inductive Breakdown Network by &lt;formula formulatype="inline"&gt;&lt;tex Notation="TeX"&gt;$X$&lt;/tex&gt; &lt;/formula&gt;-Parameters

In this paper, the $X$ -parameter measurements are applied first to establish an improved vertical bipolar inter-company (VBIC) large-signal equivalent-circuit model for silicon–germanium (SiGe) heterojunction bipolar transistors (HBTs), which can accurately describe novel and unusual characteristics of inductive behavior at breakdown that can occur in the active region under large-signal drive. This improved VBIC model presented here for SiGe HBTs is modified by incorporating a nonlinear base–collector junction breakdown network to account for the RF avalanche delay effect in the breakdown region. Good agreement between simulated and measured $X$ -parameters, which contain small-signal $S$ -parameters, large-signal spectrum, and hot $S$ -parameters, is achieved, validating the presented large-signal VBIC model in the breakdown region. The determined breakdown inductance and resistance agree well with the theoretical results. This modified model can be used to describe and predict RF large-signal performance accurately when transistors are operated in the breakdown and active regions.

Planar Schottky varactor diode and corresponding large signal model for millimeter-wave applications

A GaAs-based planar Schottky varactor diode (PSVD) is successfully developed to meet the demand of millimeter-wave harmonic generation. Based on the measured S-parameter, I–V and C–V characteristics, an accurate and reliable extraction method of the millimeter-wave large signal equivalent circuit model of the PSVD is proposed and used to extract the model parameters of two PSVDs with Schottky contact areas of 160 μm2 and 49 μm2, respectively. The simulated S-parameter, I–V and C–V performances of the proposed physics-based model are in good agreement with the measured one over the frequency range from 0.1 to 40 GHz for wide operation bias range from −10 to 0.6 V for these two PSVDs. The proposed equivalent large signal circuit model of this PSVD has been proven to be reliable and can potentially be used to design microwave circuits., planar Schottky varactor diode

An improved lumped element nonlinear circuit model for a circular CMUT cell

This paper describes a correction and an extension in the previously published large signal equivalent circuit model for a circular capacitive micromachined ultrasonic transducer (CMUT) cell. The force model is rederived so that the energy and power is preserved in the equivalent circuit model. The model is able to predict the entire behavior of CMUT until the membrane touches the substrate. Many intrinsic properties of the CMUT cell, such as the collapse condition, collapse voltage, the voltage-displacement interrelation and the force equilibrium before and after collapse voltage in the presence of external static force, are obtained as a direct consequence of the model. The small signal equivalent circuit for any bias condition is obtained from the large signal model. The model can be implemented in circuit simulation tools and model predictions are in excellent agreement with finite element method simulations.

AN IMPROVED NONLINEAR CURRENT MODEL FOR GAN HEMT HIGH POWER AMPLIFIER WITH LARGE GATE PERIPHERY

According to the characteristics of high power GaN amplifier, the common current-voltage (I-V) temperature dependence model established by Angelov is improved in this research. Besides embodying the surface temperature distribution, the most important improvement is that it can describe the current decreasing trend under high bias voltage due to trapping related dispersion and self-heating effect. The practical application shows that the prediction accuracy of the large signal equivalent circuit model is improved obviously after introducing the proposed I-V model.

CHARACTERIZATION AND MODELING OF SCHOTTKY DIODES UP TO 110 GHZ FOR USE IN BOTH FLIP-CHIP AND WIRE-BONDED ASSEMBLED ENVIRONMENTS

This paper presents a wideband model, from Direct Current (DC) to W band, for a single Anode Schottky Diode based on a commercial VDI chip. Difierent measurements have been performed to obtain a complete large-signal equivalent circuit model suitable for the device under consideration up to 110GHz, and for its integration in planar circuits. The modeling has been done using a combination of DC measurements, capacitance measurements, and RF scattering measurements. The test structure for on-wafer S- parameter characterization has been developed to obtain an equivalent circuit for Coplanar to Microstrip (CPW-Microstrip) transitions, then verifled with 3D Electromagnetic (EM) tools and flnally used to de- embed device measurements from empirical data results in W band. 3D EM simulation of the diodes was used to initialize the parasitic parameters. Those signiflcant extrinsic elements were combined with the intrinsic elements. The results show that the proposed method is suitable to determine parameters of the diode model with an excellent flt with measurements. Using this model, the simulated performance for a number of diode structures has given accurate predictions up to 110GHz. Some anomalous phenomena such as parasitic resistance dependence on frequency have been found.

Study on power characteristics of deep sub-micron SOI RF LDMOS

A large signal equivalent circuit model of SOI LDMOS is proposed. Power gain and power-added efficiency of n-type LDMOS are modeled. Deep sub-micron SOI LDMOS was fabricated and measured. We investigated the dependence of SOI LDMOS power characteristics on channel length, single gate finger width, supply voltage and working frequency. Power gain and power-added efficiency are increased by 44％ and 9％, respectively, with channel length reduction from 0.5 μm to 0.35 μm. When single gate finger width is increased from 20 μm to 40 μm, power gain and power-added efficiency of 600 μm /0.5 μm device are decreased by 23％ and 9.3％, respectively. Power-gain and power-added efficiency are increased by 13％ and 5.5％, respectively, with supply voltage increased from 3 V to 5 V. When the working frequency is increased from 2.5 GHz to 3.0 GHz, power gain and power added efficiency of LDMOS are decreased by 15％ and 4.5％, respectively.

MEXTRAM model based SiGe HBT large-signal modeling

An improved large-signal equivalent-circuit model for SiGe HBTs based on the MEXTRAM model (level 504.5) is proposed. The proposed model takes into account the soft knee effect. The model keeps the main features of the MEXTRAM model even though some simplifications have been made in the equivalent circuit topology. This model is validated in DC and AC analyses for SiGe HBTs fabricated with 0.35-μm BiCMOS technology, 1 × 8 μm2 emitter area. Good agreement is achieved between the measured and modeled results for DC and S-parameters (from 50 MHz to 20 GHz), which shows that the proposed model is accurate and reliable. The model has been implemented in Verilog-A using the ADS circuit simulator.

SiGe HBT large signal equivalent circuit model

A large signal equivalent circuit model for SiGe HBT is established based on the physical model of the transistor. The quasi saturation effect and the self-heating effect are taken into account in this equivalent circuit model. The model is composed of the intrinsic and the extrinsic parts, and has the features of clear physical meaning and simple topology. The model is embedded in the DEVEQ(Device Equations Developer) of PSPICE and simulated and analyzed by the PSPICE. The results conform to the theoretically analyzed conclusion and are in accordance with the published results in the literature.

Nonlinear Frequency-Modulation Distortion Analysis for VCO Based on Harmonic Balance Method

The analysis methods for the steady-state responses of the voltage tuning negative resistance oscillator (voltage-controlling oscillator, VCO) by the microwave nonlinear autonomous circuit harmonic balance method in millimeter-wave bands are studied in the paper. Firstly, the quasi-periodic characteristic of the steady-state response of the VCO modulated by a periodic signal is proved. Then, on the bases of the harmonic balance analysis and the inter-modulation balance analysis, a novel method for obtaining the steady-state tuning performance and the nonlinear frequency-modulation distortion characteristic of the VCO is presented. The total analysis process is aimed to a kind of NRD-guide Gunn diode VCO. The large-signal lumped equivalent circuit model of the millimeter-wave P+N-junction varactor is also given for explaining the algorithm and the principle of the NRD-guide VCO.

Implementation of nonquasi-static effects in compact bipolar transistor models

Large-signal implementation of nonquasi-static (NQS) effects in bipolar transistors is reviewed. An approach is proposed to introduce first-order NQS correction to typical quasi-static phenomenological models. Both charge- and noncharge-conserving implementations are considered. The resulted large-signal equivalent-circuit model compares well with the two-dimensional physical model in simulating HBT transient response under high-current operations. The present approach advances the state-of-the-art by allowing arbitrary bias dependence of transit times in large-signal NQS models.

Integrated high-quality rectifier-regulators

A new family of AC-DC converters is derived which integrate the functions of low-harmonic rectification, low-frequency energy storage, and wide-bandwidth output voltage control into a single converter containing one, two, or four active switches. These converters utilize a discontinuous conduction mode input inductor, an internal energy storage capacitor, and transformer secondary circuits which resemble the bridge, forward, flyback, or Cuk DC-DC converters. A large-signal equivalent circuit model for this family is presented, which uses the loss-free resistor concept. Design strategies and experimental results are given. High-performance regulation with satisfactory line-current harmonics is demonstrated with conventional duty-ratio control. Further improvements in line current are possible by simultaneous duty-ratio and switching-frequency control.

Large-signal optically controlled HEMT model and oscillator design

A new large-signal equivalent circuit model of a pHEMT with and without illumination has been developed. A HEMT oscillator operating at approximately 31 GHz has been designed and tested, based on this model. The optical tuning frequency range of 31 MHz under a halogen lamp and 60MHz under a GaAs laser illumination has been observed.