Bipolar Transistor Model Research Articles

Early effect modeling in SPICE

The approximations made in the Early effect formulation of the SPICE Gummel-Poon bipolar junction transistor (BJT) model were reasonable when the model was first developed but introduce unnecessary inaccuracies when modeling the output conductance of modern BJTs. In this paper, we give the reason the original approximations were made, present a new way to plot data to best show the Early effect, and detail a new, consistent, coupled method to determine forward and reverse Early voltages.

VBIC95, the vertical bipolar inter-company model

This paper details the VBIC95 bipolar junction transistor (BJT) model. The model was developed as an industry standard replacement for the SPICE Gummel-Poon (SGP) model, to improve deficiencies of the SGP model that have become apparent over time because of the advances in BJT process technology. VBIC95 is still based on the Gummel-Poon formulation, and thus can degenerate to be similar to the familiar SGP model. However, it includes improved modeling of the Early effect, quasi-saturation, substrate and oxide parasitics, avalanche multiplication, and temperature behavior that can be invoked selectively based on model parameter values.

Analysis and simulation of the current gain of polysilicon emitter bipolar transistors for low-temperature operation

An analytical current gain model of polysilicon emitter bipolar transistors for low-temperature operation based on the effective recombination method is presented. The model incorporates tunnelling of holes through the interface oxide layer, the reduced mobility mechanism, bandgap narrowing and carrier freeze-out effects. The low-temperature current gain and its temperature dependence are analysed numerically. The results agree well with experimental data.

過負荷保護機能を有する電流帰還型磁気マルチの解析

A detailed analysis is presented of our original overloadprotected current-feedback magnetic multivibrator. Since current-feedback magnetic multivibrators are highly efficient and are suitable for high-frequency operation, they are widely used as power sources for electronic equipment. Unlike voltage-feedback magnetic multivibrators, however, their circuits have no ability to protect themselves from overloading. We therefore proposed a new current-feedback multivibrator with overload protection. In this paper, the conditions for cessation of oscillation are derived by using our model of bipolar junction transistors. This model takes account of power dissipation, because the commonemitter static forward current transfer ratio depends on the collector current and the junction temperature.

Large-signal modeling of self-heating, collector transit-time, and RF-breakdown effects in power HBTs

A large-signal heterojunction bipolar transistor (HBT) model has been developed which includes self-heating, collector transit-time, and RF-breakdown effects. The model has a compact form which is based on a compromise between accuracy and utility. As such, the model can be readily extracted and verified with the aid of RF waveform measurements. Using the model in simulations, it was found that RF breakdown was dependent on base biasing and loading conditions. Therefore, with proper circuit design, the maximum output power of the HBT can significantly exceed the limit of open-base breakdown voltage.

SPICE modelling of impact ionisation effects in silicon bipolar transistors

A nonlocal, energy based impact ionisation model for bipolar transistors is implemented into a general purpose circuit simulator. With respect to conventional, either empirical or electric field based, models, the proposed approach enables a more physical and accurate description of impact ionisation effects in modern, high speed bipolar transistors, where non-negligible nonstationary transport effects take place as a consequence of the strong spatial variations in the electric field at the base–collector junction. The conventional base resistance model is also modified, to take into account the base resistance dependence on bias in the presence of an impact ionisation induced reverse base current. Neglecting the influence of the reverse base current on the base resistance can result in an underestimation of the degradation of both DC and switching performance of bipolar transistors due to impact ionisation. The implemented models are validated by comparison with experimental results obtained from devices of two different technologies.

I– V characteristics of the lambda bipolar transistor

The original do model of the lambda bipolar transistor proposed and the important device parameters characterized thereby are under the constraints of several approximations. It is shown to be adequate for base current drives higher than 10 μA and for devices with high values of threshold voltages. The present study provides experimental data on such devices with lower values of threshold voltages and shows them working at base current drives as low as 0.1 nA, and that these can be operated with lower supply voltages such as s V or less. These features can be exploited for suitable circuit applications. The do model of the device under these conditions needs to be suitably revised, and the issues for consideration have been identified.

Inclusion of tunneling and ballistic transport effects in an analytical approach to modeling of NPN InP-based heterojunction bipolar transistors

We describe an analytical approach to modeling NPN InP-based heterojunction bipolar transistors using a Gummel Poon model. Starting from an initial, physical description of the device's epitaxial structure and geometry, this physics-based model is utilized to simulate the device's operation using a thermionic-field-diffusion model for carrier injection at the emitter and diffusive transport across the base. This approach incorporates recent advances in understanding of device operation and improved models of parasitics. The cutoff frequency and maximum frequency of oscillation are calculated as a function of collector current density and compared with experimental measurements. For the cutoff frequency, the results of this model underestimate the high frequency performance of the device by as much as 50% at the higher collector current levels. To improve the model and to allow simulation of narrower base widths, a more rigorous analysis of tunneling through the emitter spike and ballistic transport across the base and base-collector depletion regions has been included. Quantum mechanical tunneling of electrons through the emitter-base spike has been taken into account for accurate description of the energy distribution of electron injection into the base. The resulting electron flux distribution is used as an initial distribution in a regional Monte Carlo simulator to model electron transport from the emitter edge of the base to the subcollector. The results are then used to calculate an average base transit time and base-collector space charge region delay time which can be incorporated in the analytical model.

Implementation of nonlocal model for impact-ionization current in bipolar circuit simulation and application to SiGe HBT design optimization

A nonlocal characterization of impact-ionization current is implemented in a compact but physical bipolar transistor model for predictive circuit simulation. The charge-based model, which is applicable to SiGe-base HBT's as well as Si BJT's, provides at each bias point, including ones in quasisaturation, the electric field distribution E(x) in the epi-collector, and a simplified form of the energy-balance equation enables characterization of carrier temperature T/sub e/(x) from E(x). Numerical spatial integration of the T/sub e/-dependent ionization rate yields the impact-ionization current as post-processing in the model routine. The nonlocal model is verified by applications to two advanced bipolar (HBT and BJT) technologies in which the device breakdown voltages, which are underestimated by the local-field model, are predicted. The utility of the nonlocal model in assessing design tradeoffs involving impact ionization (i.e., device breakdown versus circuit performance) is demonstrated by simulations based on the two mentioned technologies. >

Thermal and reverse base current effects on heterojunction bipolar transistors and circuits

An empirical model of a heterojunction bipolar transistor is presented. The model expands the Gummel-Poon equations to account for device self-heating, base current reversal, and the collector-emitter offset voltage. It is shown that self-heating has implications for the cutoff frequency of the HBT, for the frequency response of a small-signal amplifier, and also for the thermal stability of a current mirror circuit.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Parameter extraction for large‐signal modeling of bipolar junction transistors

AbstractA quick and efficient parameter extraction method for Si‐bipolar junction transistors, suited for nonlinear CAD, is presented. The large‐signal parameters are extracted from S‐parameter data measured at one bias point only. The model accounts for distributed base and bond wires. A comparison of simulated and measured values of reflection and transmission coefficients and nonlinear behavior of a single transistor shows the capability of the extraction method.

Compact Si1-xGex/Si heterojunction bipolar transistor model for device and circuit simulation

A physical but compact Si1-xGex/Si heterojunction bipolar transistor (HBT) model suited for device design and circuit simulation is presented. The model is based on the de Graaf-Kloosterman formalism for the modelling of the bipolar transistors, but adds important heterostructure device physics as well as physical properties of SiGe material. The model, implemented in the APLAC circuit simulator, shows how currents and charges depend on minority carrier concentrations, which in turn are functions of the heterojunction voltages. In this way, the influence of the built-in electric fields due to Ge concentration and doping density gradients, the bias-dependent transit times and the Early effect can be incorporated naturally. Comparisons between the model prediction and the experimental data for the DC current/voltage characteristics and cutoff frequencies in Si1-xGex/Si HBTs are included to demonstrate the model utility and accuracy.

Waveform-based modeling and characterization of microwave power heterojunction bipolar transistors

A waveform measurement technique has been successfully used to extract the large-signal nonlinear characteristics of microwave power heterojunction bipolar transistors. The extracted model parameters were compared to those extracted from dc and small-signal parameters in a conventional manner. It was found that, for high input drive conditions, the present model predicts a much longer collector transit time than the conventional model. Therefore, the present model is more consistent with the physical structure of the transistors and more suitable for evaluating future design improvement.

Design of analog integrated circuits and systems

MOS transistor models bipolar transistor models feedback and sensitivity in analogue integrated circuits elementary transistor stages behavioural modelling of operational and transconductance amplifiers operational amplifier design fundamentals of continuous-time and sampled-data active filters design and implementation of integrated active filters.

A new SPICE subcircuit model of power p-i-n diode

A new modeling approach for the power p-i-n diode is proposed. The base region is represented with a two-port network, obtained by solving the ambipolar diffusion equation with the Laplace transform method, and by approximating the resulting transcendental functions in the s-domain with rational approximations. Two different networks have been obtained. The first one, based on Taylor-series approximation is shown to be a generalization of a two-port model already proposed in the literature for the nonquasi-static modeling of bipolar transistors. The second network representation is based on Pade' approximation and is shown to be more accurate than the Taylor-series approach, The obtained RLC networks are easily implemented in a PSPICE subcircuit which also takes into account the emitter recombination effects and the dynamic of the space-charge voltage build-up. Good agreement has been obtained by comparing the results of the proposed model with numerical device simulations.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Power‐gain and fmax equations based on the T equivalent circuit of high‐frequency bipolar transistors

AbstractAnalytical expressions for the maximum available power gain and fmax of a high‐frequency bipolar transistor are derived from the simple T equivalent circuit model of bipolar transistors. These equations predict the power gain of the state‐of‐the‐art microwave bipolar transistor very well and show that f/max and power gain are proportional to the transconductance and decrease as the resistance‐capacitance charging time and current gain delay time increase. © 1994 John Wiley &amp; Sons, Inc.

An experimentally verified IGBT model implemented in the Saber circuit simulator

A physics-based insulated gate bipolar transistor (IGBT) model is implemented in the general-purpose circuit simulator Saber. The IGBT model includes all of the physical effects that have been shown to be important for describing IGBTs, and the model is valid for general external circuit conditions. The Saber IGBT model is evaluated for the range of static and dynamic conditions in which the device is intended to be operated, and the simulations compare well with experimental results for all of the conditions studied. >

Analytical modeling of polycrystalline silicon emitter bipolar transistors under high-level injection

We derived an analytical model, focused on injected charge storage, for electron current density J n , hole current density J ps , current gain β, and forward transit time τ f for heavily doped base and emitter with non-uniform band structures. This model can apply in high-level injection regions before the onset of the Kirk effect. By comparing with those results obtained from Sukuki's low-level injection model, it is observed that a new high-level injection term, proportional to the square of the hole current density, appears in the injected hole concentration in the polycrystalline silicon emitter and this term vanishes in the limit of low-level injection. As bias increases, J n and J p s of high-level injection model are less than those of the low-level injection model. In addition, for low-level injection model, β, τ f, the base transit time τ b, the crystalline silicon emitter transit time τ se, and the polycrystalline silicon emitter transit time τ pe keep constant for all injection region. However, for high-level injection model, β and τ b decreases as bias increases, while τ se and τ pe increase with increasing bias. τ f reaches a minimum and then increases. We conclude that the high-level injection model offers significant information for device operations at various electron current levels.

A fully analytical partitioned-charge-based model for linearly-graded SiGe-base heterojunction bipolar transistors

A fully analytical partitioned-charge-based model for linearly-graded SiGe-base heterojunction bipolar transistors

High frequency performance of SiC heterojunction bipolar transistors

A compact heterojunction bipolar transistor (HBT) model was employed to simulate the high frequency and high power performances of SiC-based bipolar transistors. Potential 6H-SiC/3C-SiC heterojunction bipolar transistors (6H/3C-HBT's) at case temperatures of 27/spl deg/C (300 K) through 600/spl deg/C (873 K) were investigated. The high frequency and high power performance was compared to AlGaAs/GaAs HBT's. As expected, the ohmic contact resistance limits the high frequency performance of the SiC HBT. At the present time, it is only possible to reliably produce 1/spl times/10/sup -4/ /spl Omega/-cm/sup 2/ contact resistances on SiC, so an f/sub T/ of 4.4 GHz and an f/sub max/ of 3.2 GHz are the highest realistic values. However, assuming an incredibly low 1/spl times/10/sup -6/ /spl Omega/-cm/sup 2/ contact resistance for the emitter, base, and collector terminals, an f/sub T/ of 31.1 GHz and an f/sub max/ of 12.7 GHz can be obtained for a 6H/3C-SiC HBT. >