Direct extraction of an empirical temperature-dependent InGaP/GaAs HBT large-signal model

A new empirical InGaP/GaAs heterojunction bipolar transistor (HBT) large-signal model including self-heating effects is presented. The model accounts for the inherent temperature dependence of the device characteristics due to ambient-temperature variation as well as self-heating. The model is accompanied by a simple extraction process, which requires only dc current-voltage (I-V) and multibias-point small-signal S-parameter measurements. All the current-source model parameters, including the self-heating parameters, are directly extracted from measured forward I-V data at different ambient temperatures. The distributed base-collector capacitance and base resistance are extracted from measured S-parameters using a new technique. The extraction procedure is fast, accurate, and inherently minimizes the average squared-error between measured and modeled data, thereby eliminating the need for further optimization following parameter extraction. This modeling methodology is successfully applied to predict the dc, small-signal S-parameter, and output fundamental and harmonic power characteristics of an InGaP/GaAs HBT, over a wide range of temperatures.     

一种新的HBT小信号模型参数优化提取法

阐述了一种新的异质结双极型晶体管（HBT）的小信号模型参数提取方法――综合多偏置点优化参数提取法. 对HBT小信号模型进行推导并确定外部参数和内部参数的计算公式;介绍了多偏置点优化算法,并在GaInP/ GaAs HBT器件上进行了鲁棒性和精确性测试. 实验采用了一系列随机初始值,结果表明提取的参数值具有唯一收敛性和精确性,仿真结果与测量数据的相对误差小于1%.     

基于MOS Model 20的RF-SOI LDMOS大信号建模

提出了一种新的基于Philips MOS Model 20 (MM20) 的RF-SOI (radio frequency silicon-on-insulator) LDMOS (laterally diffused MOS) 大信号等效电路模型. 描述了弱雪崩效应以及由热效应引起的功率耗散现象. 射频寄生元件由实验测得的S参数解析提取,并通过必要的优化快速准确地获得最终值. 模型的有效性是通过一20栅指 (每指栅长L=1μm,宽W=50μm) 体接触高阻RF-SOI LDMOS在直流,交流小信号和大信号条件下的实验数据验证的. 结果表明,直流、S参数 (10MHz~20.01GHz) 以及功率特性的仿真和实验测得数据能够很好地拟合,说明本文提出的模型具有良好和可靠的精度. 本文完成了对MM20在RF-SOI LDMOS大信号应用领域的拓展. 模型由Verilog-A描述,使用ADS (hpeesofsim)电路仿真器.     

基于MOS Model 20的RF-S0I LDMOS大信号建模

提出了一种新的基于Philips MOS Model 20(MM20)的RF-SOI(radio frequency silicon-on-insulator)LDMOS(1aterally dif-fused MOS)大信号等效电路模型.描述了弱雪崩效应以及由热效应引起的功率耗散现象.射频寄生元件由实验测得的S参数解析提取,并通过必要的优化快速准确地获得最终值.模型的有效性是通过-20栅指(每指栅长L=lμm,宽W=50μm)体接触高阻RF-SOl LDMOS在直流,交流小信号和大信号条件下的实验数据验证的.结果表明,直流、S参数(10MHz～20.01GHz)以及功率特性的仿真和实验测得数据能够很好地拟合.说明本文提出的模型具有良好和可靠的精度.本文完成了对MM20在RF-SOI LDMOS大信号应用领域的拓展.模型由Verilog-A描述,使用ADS(hpeesofsim)电路仿真器.     

Large signal modelling of GaAs/AlGaAs HBT's with separation of the surface recombination current

The effects of surface recombination on an AlGaAs/GaAs HBT have been investigated. Studies of Gummel-plots for devices with different sized base emitter junctions made it possible to separate the surface recombination from the bulk current. An extension of the Gummel–Poon model that includes this surface recombination current is suggested. The large-signal performance was evaluated by two methods, power spectrum characteristics and by design and characterization of a power amplifier. For these two measurement set-ups, measured data was compared with simulations of the model both including and excluding the surface recombination current. It is clearly seen that without including the surface recombination current, it is impossible to correctly represent the large-signal performance. The model is also verified with DC characteristics and S-parameters.     

RF CMOS modeling: a novel empirical large-signal model for an RF-MOSFET

A novel empirical model for large-signal modeling of an RF-MOSFET is proposed. The proposed model is validated in the DC, AC, small-signal and large-signal characteristics of a 32-finger nMOSFET fabricated in SMIC's 0.18 μm RF CMOS technology. The power dissipation caused by self-heating is described. Excellent agreement is achieved between simulation and measurement for DC, S-parameters (50 MHz-40 GHz), and power characteristics, which shows that our model is accurate and reliable.     

A large-signal SOI MOSFET model including dynamic self-heatingbased on small-signal model parameters

A new technique for a large-signal SOI MOSFET model with self-heating is proposed, based on thermal and electrical parameters extracted by fitting a small-signal model to measured s-parameters. A thermal derivative approach is developed to calculate the thermal resistance when the isothermal dc drain conductance is extracted from small-signal fitting. The thermal resistance is used to convert the measured dc current-voltage (I-V) characteristics containing the self-heating effects to the isothermal I-V characteristics needed for the large-signal model. Large-signal pulse and sinusoidal input signals are used to verify the model by measurement, and shown to reproduce the observed large-signal behavior of the devices with great accuracy, especially when two or more thermal time constants are used     

An investigation of the power characteristics and saturationmechanisms in HEMTs and MESFETs

A method for large-signal transistor analysis is presented. The method is based on the harmonic-balance approach but makes use of input data from measured S-parameters instead of DC or pulsed DC characteristics and a large-signal equivalent circuit with harmonic elements. The topology of this circuit is nearly identical to commonly used small-signal equivalent circuits; its application allows a detailed interpretation of the computed results, which are very precise due to the use of small-signal S-parameters. The large-signal model is applied to HEMTs and MESFETs. Their saturation mechanisms are investigated and the operational difference is discussed. The importance of including higher harmonic signal components in the large-signal analysis is also shown     

AlGaAs/GaAs HBT model estimation through the generalizedpencil-of-function method

An efficient technique of extracting the small-signal model parameters of the heterojunction bipolar transistor (HBT) is proposed in this paper. The relation between the extrinsic and intrinsic model parameters, which can be employed to drastically reduce the search space, is studied in depth. For the first time, the HBT transistor is characterized by describing S-parameters with a set of complex exponentials using the generalized pencil-of-function method. The reliable initial values of some extrinsic elements can be determined from the set of complex exponentials. This novel approach can yield a good fit between measured and simulated S-parameters     

A novel temperature-dependent large-signal model of heterojunction bipolar transistor with a unified approach for self-heating and ambient temperature effects

A large-signal modeling of power heterojunction bipolar transistor (HBT) is demonstrated for an accurate simulation of self-heating and ambient temperature effects and nonlinear behaviors such as output power, gain expansion, intermodulation distortion (IMD), and adjacent channel power ratio (ACPR). The physical relationship between the device current and the rate of change in the built-in potential with respect to the device temperature has been utilized for a fully electrothermal modeling. To enable an immediate use for a circuit design, the model extraction was done for in-situ output-stage device from two-stage power amplifier (PA) circuit. In each parameter extraction step, measurement data obtained under a consistent environment, which are current-voltage (I-V) at various temperatures and small-signal S-parameters under various bias conditions, have been carefully examined and utilized to relate the meaning of each parameter to the physical principle of the device. Measurements and simulations are compared for the verification of the model under dc condition at various temperatures.     

Thermal analysis of AlGaN-GaN power HFETs

In this paper, we present a thermal analysis of AlGaN-GaN power heterojunction field-effect transistors (HFETs). We report the dc, small-signal, large-signal, and noise performances of AlGaN-GaN HFETs at high temperatures. The temperature coefficients measured for GaN HFETs are lower than that of GaAs pseudomorphic high electron-mobility transistors, confirming the potential of GaN for high-temperature applications. In addition, the impact of thermal effects on the device dc, small-signal, and large-signal characteristics is quantified using a set of pulsed and continuous wave measurement setups. Finally, a thermal model of a GaN field-effect transistor is implemented to determine design rules to optimize the heat flow and overcome self-heating. Arguments from a device, circuit, and packaging perspective are presented.     

A simple large signal model for III–V HBT devices exceeding VBIC performances

This paper presents a large signal compact circuit simulation model for III–V heterojunction bipolar transistors (HBTs). The model is implemented as a user compiled model (UCM), in the agilent ADS circuit simulator, using C code. Though its simplicity, the model includes all physical effects taking place in power III–V-based HBT devices. It is verified by comparing its simulations to measurements in DC, small-signal and large-signal operation modes. The proposed model is further tested by comparing it to the established VBIC model and the newly introduced Agilent HBT model. It is found that despite its reduced complexity, the proposed model gives better agreement with measurements than the VBIC model in all modes of operation.     

A nonquasi-static table-based small-signal model of heterojunction bipolar transistor

A nonquasi-static table-based (NQS-TB) small-signal model, which has been used successfully in modeling FETs, is applied to a heterojunction bipolar transistor (HBT). The capacitive couplings associated with base cause the conventional model to be invalid at high frequencies. To take these effects into account, a new model is proposed that is compatible with a small-signal T-model topology. We demonstrate good agreement between the measured and simulated S-parameters over the range of 1-40 GHz.     

A parameter extraction method using cutoff measurement for alarge-scale HSPICE model of HBT's

We present an accurate parameter extraction method for the HBT large-signal equivalent circuit model in which several extrinsic parasitics are connected to HSPICE BJT model. The measured Gummel plot are used to extract DC model parameters of HBT using HSPICE. Capacitances are then obtained from S-parameter measurements of the HBTs biased to cutoff. The other parameters are determined from the active device S-parameters. The large-signal modeled Gummel plot and S-parameters show good agreement with the measured ones, respectively     

Direct parameter-extraction method for HBT small-signal model

An accurate and broadband method for the direct extraction of heterojunction bipolar transistor (HBT) small-signal model parameters is presented in this paper. This method differs from previous ones by extracting the equivalent-circuit parameters without using special test structures or global numerical optimization techniques. The main advantage of this method is that a unique and physically meaningful set of intrinsic parameters is extracted from the measured S-parameters for the whole frequency range of operation. The extraction procedure uses a set of closed-form expressions derived without any approximation. An equivalent circuit for the HBT under a forward-bias condition is proposed for extraction of access resistances and parasitic inductances. An experimental validation on a GaInP/GaAs HBT device with a 2×25 μm emitter was carried out, and excellent results were obtained up to 30 GHz. The calculated data-fitting residual error for three different bias points over 1-30 GHz was less then 2%     

Large-signal modeling and characterization of high-current effectsin InGaP/GaAs HBTs

High-current effects in InGaP/GaAs heterojunction bipolar transistors (HBTs) were modeled and characterized. In addition to the self-heating effect, high currents were found to degrade large-signal performance mainly through Kirk and quasi-saturation effects. New formalisms in terms of base transit time and base-collector diffusion capacitance were used to modify the conventional Gummel-Poon model. This new model was verified against large-signal characteristics measured at 2 GHz. The validity of the new model for HBTs of different emitter geometry was also explored     

An approach to determine small-signal model parameters for InP-based heterojunction bipolar transistors

A new method for the extraction of the small-signal model parameters of InP-based heterojunction bipolar transistors (HBT) is proposed. The approach is based on the combination of the analytical and optimization technology. The initial values of the parasitic pad capacitances are extracted by using a set of closed-form expressions derived from cutoff mode S-parameters without any test structure, and the intrinsic elements determined by using the analytical method are described as functions of the parasitic elements. An advanced design system is then used to optimize only the parasitic parameters with very small dispersion of initial values. Good agreement is obtained between simulated and measured results for an InP HBT with 5/spl times/5 /spl mu/m/sup 2/ emitter area over a wide range of bias points up to 40 GHz.     

Hot small-signal S-parameter measurements of power transistors operating under large-signal conditions in a load-pull environment for the study of nonlinear parametric interactions

This paper presents a setup that enables wide-band (in-band and out-of-band) measurements of hot small-signal S-parameters of nonlinear devices driven by a large-signal single tone (namely, the pump signal). A load-pull characterization is performed at the pump frequency (F/sub 0/), while hot small-signal S-parameters are measured with a perturbating signal at a frequency (f) by the use of a probe tone. Basically, the frequency of the probe tone is swept over a wide bandwidth (at the present time from 300 MHz up to F/sub 0//2). A higher frequency range, from near dc to KF/sub 0/, will be implemented in a similar manner. The measurement setup reported here is applied to on-wafer measurements of S-band HBTs. Hot small-signal S-parameter measurements versus large-signal load impedance and pump level will be shown. An application to the prediction of parametric oscillations will be demonstrated. A parametric oscillation predicted at 373 MHz is confirmed by spectrum measurements.     

Consistent modeling of capacitances and transit times of GaAs-based HBTs

This paper investigates how time delays and capacitances observed under small-signal conditions can be consistently accounted for in heterojunction bipolar transistor (HBT) large-signal models. The approach starts at the circuit level by mapping the large-signal equivalent circuit (which consists of charge and current sources) to the well-known small-signal circuit (which consists of capacitances, transit-time, and resistances). It is shown that and how bias dependent charge sources at either pn-junction impact transit-time, base-collector capacitance, and their mutual dependence. It is demonstrated for the example of a GaAs-based HBT that the interrelation of the elements is observed in measurements as predicted. The results of the investigation enhance understanding of HBT model characteristics and provide a criterion to check model consistency.