Modeling the bias and temperature dependence of a C-class MESFETamplifier

In this paper, a complete bias and temperature-dependent large-signal model for a MESFET is determined from experimental S-parameters and dc measurements. This model is used in the analysis of the performance of a C-class amplifier at 4 GHz over a -50° to 100°C temperature range and for different bias conditions. The dependencies of the elements of the equivalent circuit, as well as the amplifier gain on the temperature and the operating point, are evaluated. The gain optimization and the analysis as a function of temperature of the MESFET amplifier are done by using the describing function technique. Optimum bias device conditions in the C-class are obtained for maximum gain and also the flattest gain versus input power rate. A comparison between theoretical and measured results over temperature and bias ranges is shown. Experimental results show an excellent agreement with the theoretical analysis     

An approach to determining an equivalent circuit for HEMTs

A simple way to determine a small-signal equivalent circuit of High Electron Mobility Transistors (HEMTs) is proposed. Intrinsic elements determined by a conventional analytical parameter transformation technique are described as functions of extrinsic elements. Assuming that the equivalent circuit composed of lumped elements is valid over the whole frequency range of the measurements, the extrinsic elements are iteratively determined using the variance of the intrinsic elements as an optimization criterion. Measurements of S-parameters up to 62.5 GHz at more than 100 different bias points confirmed that the HEMT equivalent circuit is consistent for all bias points     

Bias dependence of the MODFET intrinsic model elements values atmicrowave frequencies

S-parameters of MODFETs were measured versus bias instead of frequency with a special feature of the HP8510 network analyzer. Figure of merit plots, f_T, and f_max, were quickly generated from the bias sweeps of S-parameters, and optimum bias points were easily found. The intrinsic device elements of MODFETs were calculated after de-embedding the measurements from the device parasitics. The technique is demonstrated with a 0.15-μm pseudomorphic MODFET with an f_T of 150 GHz. The usefulness of the technique for understanding the operation of the MODFETs is discussed. With this technique a bias scan of an intrinsic element value can be measured and plotted in 13 s     

A technique for modelling S-parameters for HEMT structuresas a function of gate bias

A physically based technique for modeling HEMT structure S-parameters is presented. The core of the model is directly dependent on the HEMT wafer structure and the physical gate length. The model accurately predicts the device's S-parameters as a function of the applied gate bias. The physical basis facilitates the modeling of different types of HEMT structures. Measured S-parameters and simulation results over a frequency range of 1 to 25 GHz are presented for three different HEMT structures: uniformly doped, GaAs channel; pulse-doped, GaAs channel; and uniformly doped, strained InGaAs channel     

A novel, bias-dependent, small-signal model of the dual-gate MESFET

A dual-gate MESFET from NEC (NE25000) has been measured and modeled. S-parameters and drain-to-source currents calculated from the model are in good agreement with measured data. The model consists of a cascode of two intrinsic, single-gate, nonlinear FET-models embedded in a network representing the device parasitics. A step-by-step procedure has been used to determine the 47 parameters of the model. DC-measurements were used to find starting values for some of the parameters of the nonlinear models. The parasitic capacitances were determined from three-port S-parameters measured at V_DS=0 V, I_DS=0 A and V(G₁S)=V(G₂S)=-4.0V. The parasitic inductances and resistances were determined from S-parameters measured at the same bias-point but with forward-biased gates, and from DC-measurements. The final model-optimization was done by simultaneously fitting the model to drain-to-source currents and three-port S-parameters measured at several different, active bias-points (V_DS >0)     

一种新的HEMT小信号模型参数提取方法

介绍了一种高电子迁移率晶体管(HEMT)的小信号参数提取方法——综合多偏置点优化参数提取法。该文首先推导并提出了器件的模型、确定外部参数和内部参数，其次介绍了多偏置点优化算法。最后，以PHEMT器件为例进行鲁棒性和精确性测试，实验采用一系列随机起始值，结果表明，提取的参数值与经验值相差小于1％。     

基于神经网络的HEMT大信号模型

运用人工神经网络技术建立了高电子迁移率晶体管(HEMT)的大信号模型。通过脉冲I-V测试和测量不同偏置条件下的S参数,获得了大信号等效电路模型中寄生参数和非线性本征元件的数值。通过BP神经网络,利用偏置相关的非线性元件值作为训练样本,利用误差反向传播的Levenberg-Maquardt方法训练神经网络并得到了网络权重数据。模型中的非线性元件在CAD软件中用神经网络实现,并将权重数据和CAD软件结合进行仿真。测试和仿真结果表明模型具有很高的精度。     

A pure analytic method for direct extraction of collector-up HBT's small-signal parameters

A pure analytic procedure for direct extraction of the small-signal equivalent-circuit parameters, including extrinsic inductances, has been demonstrated and successfully applied to III-V and SiGe collector-up heterojunction bipolar transistors (HBTs). This method can alleviate some difficulties encountered among conventional extracting techniques that are the use of additional test structures, forward-biased measurements at specific bias conditions, and empirical optimization process. In this paper, the hybrid-/spl pi/ equivalent-circuit elements are extracted in a simple and efficient way from impedance and admittance formulation on the basis of measured S-parameters. To study the bias dependence, the extrinsic and intrinsic circuit components are evaluated under different bias conditions. The model parameters are sequentially derived during the extraction process yielding a full set of physical element values. The validity of our model is explored on pnp collector-up AlGaAs-InGaAs HBTs, and a good coincidence between measured and modeled S-parameters is observed for the entire frequency range of operation. Consistent extracted trends indicate that this improved equivalent-circuit model is suitable to be implemented in circuit simulators for microwave-circuit TCAD applications.     

A Simplified Microwave Model of the GaAs Dual-Gate MESFET

A simplified wide-band model of the GaAs dual-gate MESFET based upon the familiar cascode representation is presented, which is valid over the frequency range of 2-11 GHz. The equivalent circuit contains 14 elements and the parameter values are directly determined from 3-port S-parameters over the frequency range of 4-6 GHz, and dc data. Separate microwave measurements of each FET part are not required, thus greatly reducing the number of measurements required to fully characterize the device. The method has been used to model a GaAs dual-gate MESFET in which both FET parts were in the saturation region, and good agreement has been obtained between measured and calculated results without the need for computer optimization.     

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.     

An accurate photonic capacitance model for GaAs MESFETs

A new set of pseudoempirical equations is presented in order to simulate the optical and bias dependencies of GaAs MESFET junction capacitances, which is valid for the whole I-V plane. The variations induced in the small-signal equivalent circuit by the optical illumination are extracted from on-wafer scattering parameter measurements. New linear and quasi-logarithmic variations versus the incident optical power are shown for gate-drain and gate-source (Cgd and Cgs) capacitances. Furthermore, experimental results are in very good agreement with the simulated values for a wide range of optical power and bias conditions. Large signal MESFET models show a better fit with measured S-parameters than those previously published, leading to a greater degree of confidence in the design of photonic monolithic microwave integrated circuits     

Nonlinear models for the intermodulation analysis of FET mixers

An accurate, detailed analysis program has been developed for intermodulation distortion (IMD) simulation of FET mixers. This program is very efficient at calculating the IMD from multiple RF inputs. We have proposed a simplified nonlinear model for IMD analysis of FET gate mixers. The accuracy of the simplified model has been verified experimentally using two different MESFET mixers and one HEMT mixer at X band. All the tests show good agreement between measured results and the calculated results for second- and third-order IMD. The simplified model is based on modeling the derivative of the device transconductance by a sum of a Gaussian function and a linear function of the gate voltage. Drain bias dependence is ignored. The advantage of this model is that it can be used for both MESFET and HEMT mixers, and its fitting parameters can be easily determined from a nonlinear characterization of the devices at low frequencies     

一种基于半分析法的HEMT小信号参数的提取方法

提出了一种基于半分析法的高速电子迁移率半导体晶体管小信号模型的提取方法.此方法是用测试结构的方法来提取焊盘电容和寄生电感,半分析法来提取寄生电阻,提高了寄生电阻的提取精度.在频率高达40 GHz的范围内,多偏置情况下模拟的S参数和测试的S参数曲线吻合良好,证明这种方法是正确的.     

Fast and efficient extraction of HBT model parameters usingmultibias S-parameter sets

Accurate parameter extraction technique has been presented for a small-signal equivalent circuit model of AlGaAs-GaAs HBT's. This technique makes use of multibias data optimization regarding two sets of S-parameters in the active mode and one in the cut-off mode, under the physics-based constraint that current-dependent elements in two active bias circuits are linked to each other by the ratio of their currents. This multibias optimization as well as the constraint imposed on intrinsic parameters may reduce the degree of freedom of circuit variables and increase the probability of finding a global minimum result. As a result of this extraction, good agreement is seen between the circuit models and their measured S-parameters in the frequency range of 0.045 to 26.5 GHz     

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%     

AlGaN/GaN高电子迁移率晶体管小信号等效电路的参数提取

本文在高电子迁移率晶体管(HEMT)小信号等效电路模型的基础上,考虑了AlGaN/GaN HEMT的结构特性,具体分析了寄生参数和本征参数的提取方法.采用这些方法,实际测量了5～10 GHz频率下HEMT器件的小信号S参数并提取了它的电学参数,S参数的计算值与实际测量值进行了比较.实验结果表明此方法简单易行,较为精确.     

Analytical parameter extraction of the HBT equivalent circuit withT-like topology from measured S-parameters

A pure analytical method for extraction of the small-signal equivalent circuit parameters from measured data is presented and successfully applied to heterojunction bipolar transistors (HBT's). The T-like equivalent circuit is cut into three shells accounting for the connection, and the extrinsic and intrinsic parts of the transistor. The equivalent circuit elements are evaluated in a straightforward manner from impedance and admittance representation of the measured S-parameters. The measured data are stripped during the extraction process yielding, step by step, a full set of circuit elements without using fit methods. No additional knowledge of the transistor is needed to start the extraction process with its self-consistent iteration loop for the connection shell. The extrinsic and intrinsic equivalent circuit elements are evaluated using their bias and frequency dependencies. This method yields a deviation of less then 4% between measured and modeled S-parameters     

Validation of a nonlinear transistor model by power spectrumcharacteristics of HEMT's and MESFET's

The bias dependence of the power output spectrum and the generation of intermodulation products from different HEMT's and MESFET's at large signal excitation is studied and compared with simulated values. An extended HEMT/FET model suitable for small and and negative V_ds (with a drain voltage dependence of the peak transconductance in the unsaturated drain current region, and at negative drain voltage), is also proposed. Good agreement between simulated and measured power spectrum up to at least the fourth harmonic is demonstrated for HEMT and MESFET devices from different manufacturers. Measured and simulated intermodulation products are also in good agreement, which confirm the validity of the model     

Modelling drain and gate dependence of HEMT 1-50 GHz, small-signalS-parameters, and d.c. drain current

We present refinements to a previously validated HEMT model that improves the model's accuracy as a function of drain bias for simulating d.c. drain current and 1-50 GHz, small-signal S-parameters. By comparing simulation data with experimental data for a 0.4-μm-gate pseudomorphic HEMT, we have been able to establish the accuracy of the refined model, which predicts the device's d.c. current and S-parameters as a function of the applied drain and gate biases to within an accuracy of ~5%. The core of the model and, in particular, its bias dependence, are directly dependent on the HEMT wafer structure and the physical gate length     

用改进的遗传算法精确提取GaAs MESFET小信号等效电路参数

提出了一种改进的遗传算法 ,应用于提取 Ga As MESFET小信号等效电路参数 .改进的算法采用浮点编码连续突变 ,多种遗传操作合作运行 ,并应用子代优化策略克服了传统遗传算法可能出现的种群退化现象 ,该算法可快速搜索到全局最优解而不受初始值限制 .在 0 .1～ 1 0 GHz范围内实现了精确、快速地提取 Ga As MESFET小信号等效电路参数 ,并可合理外推至 2 0 GHz,整个过程无需人工干预 .算法用 Matlab语言实现 ,可方便地应用于 HBT和HEMT以及无源元件电容、电感的参数提取