Optimal second-order small-signal model for long- and short-channelthree-terminal MOSFET/MODFET wave equation

An optimal second-order small-signal model is developed for the long-channel three-terminal MOSFET/MODFET wave equation. The resulting Y parameters admit the correct fourth-order frequency power series expansion and exhibit a graceful degradation at high frequencies compared to a previously reported second-order model. This model can be integrated in the velocity-saturated MOSFET/MODFET equivalent circuit and is demonstrated to greatly improve the frequency range of validity of this short-channel model. The excellent results obtained demonstrate the validity of both the equivalent-circuit synthesis procedure and the correctness of the equivalent circuit proposed     

Deep-submicrometer DC-to-RF SOI MOSFET macro-model

We present a submicrometer RF fully depleted SOI MOSFET macro-model based on a complete extrinsic small-signal equivalent circuit and an improved CAD model for the intrinsic device. The delay propagation effects in the channel are modeled by splitting the intrinsic transistor into a series of shorter transistors, for each of which a quasistatic device model can be used. Since the intrinsic device model is charge-based, our RF SOI MOSFET model can be used in both small and large-signal analyses. The model has been validated for frequencies up to 40 GHz and effective channel lengths down to 0.16 μm     

Analytic solution of the velocity-saturated MOSFET/MODFET waveequation and its application to the prediction of the microwavecharacteristics of MODFETs

An AC model for the saturated MODFET is reported. The MOSFET/MODFET wave equation accounting for velocity saturation and channel length modulation is derived. An exact solution of the wave equation is obtained in terms of Bessel functions. A frequency power series is used to derive analytic expressions for the intrinsic Y -parameters. This AC model is applied to the prediction of the microwave characteristics of 1-μm AlGaAs/GaAs MODFETs and GaAlAs/InGaAs/GaAs pseudomorphic MODFETs. The parameters used by the AC model are extracted by fitting the I-V characteristics. The parasitics are either estimated or measured. A good prediction of the scattering parameters measured from 2 to 18.4 GHz is achieved for different biases. The deviation of the calculated unilateral power gain from the measured values was on average 1.25 and 2.18 dB for the conventional MODFET and the pseudomorphic MODFET, respectively     

SiGe HBT非准静态小信号等效电路的参数提取

提出了一种硅锗异质结双极型晶体管（SiGe HBT）非准静态效应的小信号等效电路模型的参数提取方法。整个参数提取过程建立在由非准态效应的小信号等效电路推导出的一系列泰勒级数解析公式并结合参数直接法,该方法依赖于测量的S参数,不使用任何的数值优化法,参数提取结果使用CAD仿真验证。结果表明该参数提取方法简单易行,较为精确,该方法能够用到不同工艺SiGe HBT参数提取。     

A robust and physical BSIM3 non-quasi-static transient and ACsmall-signal model for circuit simulation

A new non-quasi-static (NQS) MOSFET model, which is applicable for both large-signal transient and small-signal ac analysis, has been developed. It employs a physical relaxation time approach to take care of the finite channel charging time to reach equilibrium and the effect of instantaneous channel charge re-distribution. The NQS model is formulated independently from the dc I-V and the charge-capacitor model, thus can be easily applied to any existing simulators. The model has been implemented in the newly released BSIM3 version 3, and comparison has been made among this model, common quasi-static (QS) SPICE models and PISCES two-dimensional (2-D) numerical device simulator. While predicting accurate NQS behavior, the time penalty for using the new model is only about 20-30% more than the common QS models. It is much less than the time required by other NQS models reported. Limitations and compromises between simplicity, efficiency and accuracy are also discussed     

A new method for determining the FET small-signal equivalentcircuit

A method to determine the small-signal equivalent circuit of FETs is proposed. This method consists of a direct determination of both the extrinsic and intrinsic small-signal parameters in a low-frequency band. This method is fast and accurate, and the determined equivalent circuit fits the S-parameters well up to 26.5 GHz     

Small-signal characteristics of n+-Ge gate AlGaAs/GaAsMISFET's

The small-signal characteristics have been clarified by S-parameter measurements and equivalent circuit modeling. A large intrinsic transconductance of 630 mS/mm and a maximum cutoff frequence f_T of 70 GHz have been achieved for a MISFET with a gate length of 0.4 μm. The average electron drift velocity in the channel, evaluated from the f_T, was as high as 1.7×10⁷ cm/s. In obtaining an equivalent-circuit model, a gate conductance parallel to the gate-source capacitance is introduced to take into account the gate forward current of normally-off FETs The gate conductance does not cause the f _T of the MISFET to deteriorate due to a small gate forward current at a large gate bias, in contrast to GaAs MESFETs     

Modeling of on-state MOSFET operation and derivation of maximumchannel field

A novel approach to modeling MOSFET operation in the threshold region is proposed. A two-dimensional Poisson equation is solved analytically and the current continuity equation is solved iteratively in a self-consistent feedback scheme. The I-V characteristics and the profiles of channel field and mobile charge sheet are found over the entire region of device operation. The boundary between linear and saturation regions of device operation is inherently nonexistent in the model. The physical mechanism underlying the high values of maximum channel field E_L beyond channel pinch-off is highlighted. A simple analytical E_L model is derived. A comparison of this E_L model with previous models is made in the context of the experimental data     

The voltage-doping transformation: a new approach to the modelingof MOSFET short-channel effects

It is shown that the influence of the drain-source field on the potential barrier height is physically equivalent to and can be replaced by a reduction in channel doping concentration according to a formula derived from the two-dimensional Poisson equation. The actual barrier height for any drain bias and channel length, on which the derived equation depends, can be calculated easily using well-known one-dimensional (long-channel) solutions. This simple but general procedure, called the voltage-doping transformation (VDT), is shown to lead to analytically calculated potential distributions in fairly good agreement with two-dimensional numerical simulation. An application of the VDT to threshold voltage (V_tj) calculations also is shown. The V_th model is compared with measurements taken on implanted n-MOSFETs with various channel lengths. Good agreement demonstrates the accuracy of both the VDT and the new V_th model     

Small-signal MOSFET models for analog circuit design

Presents first-order large-signal MOSFET models and derives corresponding small-signal models. The parameters of the small-signal models are related to operating-point bias and to the parameters of the IC process used to fabricate the device. The impact upon small-signal performance of many second-order effects present in small-geometry MOSFETs is explored. A representative analog circuit, fabricated with a 1 /spl mu/m feature-size NMOS technology, is analyzed using the small-signal models derived. Results of approximate analysis, without the use of computer aids, are compared with detailed computer simulation results.     

Direct extraction of the AlGaAs/GaAs heterojunction bipolartransistor small-signal equivalent circuit

The authors describe a novel, direct technique for determining the small-signal equivalent circuit of a heterojunction bipolar transistor (HBT). The parasitic elements are largely determined from measurements of test structures, reducing the number of elements determined from measurements of the transistor. The intrinsic circuit elements are evaluated from y-parameter data, which are DC-embedded from the known parasitics. The equivalent-circuit elements are uniquely determined at any frequency. The validity of this technique is confirmed by showing the frequency independence of the extracted circuit elements. The equivalent circuit models the HBT s-parameters over a wide range of collector currents. Throughout the entire 1-18-GHz frequency range, the computed s-parameters agree very well with the experimental data     

Broad-band determination of the FET small-signal equivalent circuit

A method to determine the broadband small-signal equivalent circuit of field-effect transistors (FETs) is proposed. This method is based on an analytic solution of the equations for the Y parameters of the intrinsic device and allows direct determination of the circuit elements at any specific frequency or averaged over a frequency range. The validity of the equivalent circuit can be verified by showing the frequency independence of each element. The method can be used for the whole range of measurement frequencies and can be applied to devices exhibiting severe low-frequency effects     

A nonquasi-static MOSFET model for SPICE-transient analysis

The long-channel MOSFET model is based on an approximate solution to the nonlinear current-continuity equation in the channel. The model includes the large-signal transient and the small-signal AC analyses, although only the transient model is reported here. Comparisons have been made between this model and the 1-D numerical solution to the current-continuity equation, 2-D device simulation (PISCES), and the quasistatic (QS) results. The channel-charge partitioning scheme in the charge-based QS models is shown to be inadequate for the fast transient. This model does not use a charge-partitioning scheme and the currents are dependent on the history of the terminal voltages, not just the instantaneous voltages and their derivatives. For the slow signals (compared to the channel transit time), the nonquasistatic (NQS) model is reduced to the quasistatic 40/60 channel-charge partitioning scheme. The CPU time required for this model is about two to three times longer than that of conventional MOSFET models in SPICE     

B-Spline Based, Large-Signal DC and Microwave-Model for SOI MOSFETs

We present a large/small-signal, non-quasi-static, charge conserving, SOI MOSFET modeling technique suitable for DC and high frequency circuit design. The device model is extracted from small signal microwave iso-thermal Y-parameter data and DC I–V characteristics. Low frequency dispersions associated with self-heating and floating body effects are verified to not limit the performance of this technique since it relies on both DC and transient I–V characteristics. The technique is applied to the modeling of a short-channel, partially depleted, SOI nMOSFET simulated on PISCES. The model generated is incorporated into a circuit simulator, which is used to perform large-signal transient and harmonic balance simulations. The transient I–V and gate charge extracted from the iso-thermal small-signal microwave Y-parameters, are in excellent agreement with the iso-thermal transient I–V and gate charge obtained from PISCES, respectively. The model topology is extended with a parasitic bipolar sub-circuit which automatically calculates the DC operating point for self-biasing circuits. Transient and non-linear power characterization results predicted with this model agree well with those obtained from PISCES for a wide range of input power drives. A complete electro-thermal model is proposed and verified to be able to predict temperature and transient I–V response.     

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.     

A simple subcircuit extension of the BSIM3v3 model for CMOS RFdesign

An accurate and simple lumped-element extension of the BSIM3v3 MOSFET model for small-signal radio-frequency circuit simulation is proposed and investigated. Detailed comparisons of the small-signal y and s parameters with both two-dimensional device simulations and measurement data are presented. A procedure is developed to extract the values of two lumped resistors-the only added elements. The non-quasi-static and substrate effects can be modeled with these two resistors to significantly improve the model accuracy up to a frequency of 10 GHz, which is about 70% of the f_T of the 0.5 μm NMOS transistor     

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     

Modeling the gate I/V characteristic of a GaAsMESFET for Volterra-series analysis

The authors show that the Taylor-series coefficients of a FET's gate/drain I/V characteristic, which is used to model this nonlinearity for Volterra-series analysis, can be derived from low-frequency RF measurements of harmonic output levels. The method circumvents many of the problems encountered in using DC measurements to characterize this nonlinearity. This method was used to determine the incremental gate I/V characteristic of a packaged Aventek AT10650-5 MESFET biased at a drain voltage of 3 V and drain current of 20 mA. The FET's transconductance was measured at DC, and its small-signal equivalent circuit (including the package parasitics) was determined by adjusting its circuit element values until good agreement between calculated and measured S parameters was obtained. The FET was then installed in a low-frequency test fixture. Excellent results were obtained     

Parameter extraction from I-V characteristics ofsingle MOSFETs

A method is presented to extract the bias-dependent series resistances and intrinsic conductance factor of individual MOS transistors from measured I-V characteristics. If applied to groups of scaled channel length devices, it also allows determination of the effective channel length together with the transversal field dependence of the carrier mobility. The method is exactly derived from conventional MOS theory based on the gradual channel approximation, and the deviations from such an ideal case are studied by means of two-dimensional device simulations. Experimental results obtained with n- and p-channel transistors of conventional as well as LDD type are presented to show the correctness of the proposed extraction procedure     

考虑速度过冲效应的HEMT物理模型

本文提出了一种考虑这冲效应的ＨＥＭＴ器件静态和小信号解析物理模型。通过对栅极下面道中造近源端附近的电场采用弱强梯场近似，提出了一个半经验的速度过冲模型，在非线性电荷控制模型的基础上述导出了基于物理参数的ＨＥＭＴ器件电流－电压特性和小等效电路参数的解析表达式。实际计算结果与测得数据比较表明，本模型具有比较高的精度。