Simulating the current mirror with a self-heating BJT model

A Gummel-Poon (GP) BJT (bipolar junction transistor) model that includes self-heating is presented, and a current-mirror circuit is used to show its significance. Self-heating thermal effects are modeled by a simple electrical analog circuit, which also provides BJT junction temperature as part of the CAD solution. Both discrete-BJT and IC mirror circuits are tested. The self-heating model correctly simulates the temperature stability of the IC mirror circuit where the BJTs are in close thermal proximity. For the discrete-BJT circuit, a standard GP model produces errors up to 84% versus 6.1% for the self-heating model     

The effects of BJT self-heating on circuit behavior

This study demonstrates the circuit and device conditions under which self-heating can significantly affect bipolar junction transistor (BJT) circuit behavior. Simple quantitative measures are supplied that allow estimation of thermally induced errors in BJT small-signal parameters, based on knowledge of the transistor geometry and its Early voltage. It is shown that errors in output admittance and reverse transadmittance can be significant without much power dissipation, especially when the base and emitter driving impedances are small. Other small-signal parameters are less affected unless the power dissipation becomes significant. Thermal effects in large-signal DC analysis can be significant in precision analog circuits that depend on close transistor matching; such circuits can also exhibit long settling-time tails due to long thermal time constants. ECL (emitter-coupled logic) delay is shown to be insensitive to self-heating. These effects are demonstrated through simulations of a variety of circuits using versions of SPICE modified to include physics-based models for thermal impedance     

硅双极型晶体管的可缩放MEXTRAM模型及参数提取

文章在分析Mextram模型缩放性的基础上,介绍了可缩放Mextram模型的参数提取方法.结合不同几何尺寸的硅双极型晶体管的测试数据,进行了参数提取.得到的可缩放Mextram模型的仿真结果与测试数据吻合得很好.     

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%     

A non-quasi-static small-signal model for metal-semiconductor junction diodes

The quasi-static approximation, which assumes that free-carrier propagation delay in the semiconductor device is zero, is often used in device modeling. Consequently, the quasi-static model is adequate only for low-frequency excitations for which free-carrier propagation delay is very small compared to the variation of the excitations. This paper develops a non-quasi-static model suitable for metal-semiconductor junction diodes subjected to small-signal excitation. We show that the predictions of the non-quasi-static model agree more favourably with experimental data taken from Al---Si diodes than that of the quasi-static model, particularly when the frequency of the excitation is high.     

An accurate small-signal model for AlGaN-GaNHEMT suitable for scalable large-signal model construction

The validity of the proposed small-signal model (SSM) and the developed extraction method in for large GaN devices is investigated. Extraction of parasitic elements is performed for different size devices to show the scaling of these elements with the gate width. The model shows a very good result for describing the parasitic distributed effect, which is considerable for large devices.     

SPICE model and parameters for fully-depleted SOI MOSFET'sincluding self-heating

A simple methodology to accurately extract constant temperature model parameters from static measurements of fully-depleted SOI MOSFET current-voltage characteristics is demonstrated. Self-heating is included in an existing physically-based, short-channel bulk MOSFET model, PCIM, by allowing the temperature to change linearly with power dissipation at each bias point. Only a simple modification of the channel bulk charge in PCIM is necessary to adapt it for SOI. The temperature dependence of the physical parameters (mobility, flatband voltage, and saturation velocity) are also fitted and included in the model. Excellent fit to experimental fully-depleted SOI data is shown over a large range of bias conditions and channel lengths. Once the static SOI data is fitted, the constant temperature model parameters appropriate for circuit simulation are easily extracted     

Refined small-signal model in DCM for constant off-time control

The conventional small-signal model in the discontinuous conduction mode for constant off-time control becomes increasingly inaccurate as the conversion ratio increases. A new model is proposed which takes account of the fact that the switching interval is not constant     

Determination of a small-signal model for ion-implanted microwave transistors

Most microwave transistor models are useful within specific frequency ranges; outside those ranges, they become inaccurate essentially because of the distributed nature of the active base resistance which is modeled as a lumped element. In this paper, a quantitative study of the two-dimensional current flow in the active region of an ion-implanted device leads to the synthesis of a small-signal model, emphasizing its relations to the distributed parameters defined. Methods for extracting those parameters are proposed via expressions that relate them to electrical measurements at the terminals. A final section deals with the analysis of experimental data to verify the validity of a distributed equivalent circuit at frequencies up to 10 GHz.     

Procedure for building a MOS transistor high frequency small-signal model

This paper examines a procedure for building a MOS transistor small-signal equivalent circuit for the high frequency range. Procedures are proposed for determining the ac and dc parameters. The simulation results and experimental data are also presented.     

一种新颖的HEMT小信号模型参数直接提取方法

建立了一套完整的直接提取高电子迁移率器件(HEMT)小信号模型等效电路参数的新方法。采用Open去嵌图形对器件寄生电容进行近似提取,避免了ColdFET方法提取的寄生参数为负值的现象;通过Yong Long方法对寄生源电阻进行提取,减少了模型参数提取复杂度。与其它文献报道的小信号模型参数提取方法相比,该方法物理意义简明清晰,提取速度快,并且对新材料、新器件结构有较强的实用性。     

An analytical small-signal bias-dependent nonuniform model for p-i-n traveling-wave photodetectors

A fully analytical small-signal model is developed for the frequency response of traveling-wave photodetectors. It takes into account the dependence of the equivalent transmission-line admittance on the position, induced by the nonuniform distribution of the optical beam along the traveling direction. Moreover, the influence of the bias voltage on the transit time has been accurately investigated. The model is applied to the design of an InAlAs-InGaAs p-i-n photodetector. Its performances are investigated in term of electrical bandwidth.     

Simulation and modeling-a CAD model for the BJT with self heating

A Gummel-Poon model that accounts for self heating in the bipolar-junction (BJT) transistor is presented. The model uses a simple but flexible RC analog circuit for thermal effects. Junction temperature as a voltage is a byproduct of the modeling approach. In contrast to the standard model, this model does not require changes in BJT parameters in order to track circuit changes that affect BJT dissipated power. Although not presented here, transient behavior due to self heating and thermal capacitance has been tested, and it is also correctly predicted by this model     

一种新颖的HBT小信号模型参数直接提取方法

提出了一种改进了的HBT小信号参数直接提取的方法。该方法中在提取极间寄生参数的基础上采用fly-back技术提取发射极和集电极电阻,降低了传统的采用集电极开路的方法提取全部电阻参数的复杂度,并且建立了一套完整的直接提取HBT小信号模型的新方法。与文献报道的小信号模型参数提取的方法相比,该方法的优点是,提取过程具有简明清晰的物理意义,提取速度快,并且具有较好的精度和较宽频带范围的可实用性。     

A.C. small-signal model for bipolar transistors in saturation

A modified charge-control theory is used to derive a small-signal equivalent circuit which is valid in saturation. From this circuit can be deduced the fT(Ic) and the transconductance gfb(Ie), for example, which are compared with measurements. A short discussion of the results is given.     

A physically based small-signal circuit model for heterostructureacoustic charge transport devices

A physically based small-signal circuit model for GaAs-AlGaAs Schottky gate heterostructure acoustic charge transport (HACT) devices is presented. Analytical expressions for the instantaneous and average channel current as a function of gate voltage are obtained from physical device parameters. The charge injection model is based on subthreshold current models for GaAs MESFETs. It is shown that the shape of the sampling aperture of the charge injection operation is approximately Gaussian. Good agreement is obtained between the measured DC channel current versus gate voltage and that predicted by the model. Equivalent circuits for the transfer and output sensing operations and expressions for noise sources due to the physical processes that occur within the device are developed. Thermal, shot, and transfer noise are treated. The form of the analytic expressions for frequency response and noise figure allows easy implementation on commercially available CAE software. Simulations of both gain and noise figure performed on Libra show good agreement with measured data     

Scalable RF MIS varactor model

A scalable varactor model based on the equations in the BSIM3v3 model (Berkeley short-channel IGFET model) is presented to model the behaviour of a silicon,based metal-insulator-semiconductor (MIS) varactor with different device geometries and bias conditions at different operation frequencies. The root mean square (RMS) errors of the S-parameters between the measured and simulated data are less than 3%. The scalable model provides satisfactory performance prediction for realising silicon radio frequency integrated circuits (RFICs)