Computer-Aided Determination of the Small-Signal Equivalent Network of a Bipolar Microwave Transistor

The actual technology for the production of transistors is now suitable for bipolar transistors in the 10-GHz range. In order to obtain amplifier circuits in this microwave range, the knowledge of the exact equivalent circuit is essential. A computer method for the determination of the equivalent network is given. The final application and accuracy are shown for a particular microwave transistor.     

The effects of carrier-velocity saturation on high-current BJToutput resistance

Modern bipolar junction transistors (BJTs) tend to operate with saturated carrier velocity in the collector space-charge region. A physical analysis of the effects of velocity saturation on the output resistance of BJTs, especially for high current levels is presented. Physical analyses show that when the collector current density approaches a critical value, the Early voltage can increase significantly due to carrier-velocity saturation as the resulting base push-out partially offsets base-width modulation. This effect is also demonstrated in simulations with PISCES and MMSPICE     

A Practical Tantalum Thin-Film Single-Sideband Demodulator Using RC Time-Varying and Active Networks

The thin-film circuit described in this paper is equivalent to a demodulator circuit containing an extremely selective filter ("sideband" filter). Such a filter would, in conventional form, require very high Q inductors or, as the Q requirement increases, the use of crystal or mechanical filters. At the frequency of operation of this circuit (1 MHz), demodulation with conventional filters would have to be accomplished in two or more stages so that the selectivity requirement can be decreased for each filter. Thin-film techniques restrict us to circuits using only resistors (R), capacitors (C), and added semiconductor devices (thin-film inductors are not considered here since their inductance values are too small). The current trend is to realize frequency selective networks (conventionally in LC form) as active RC networks. However, although the circuit described here incorporates such a network, the main selectivity requirement cannot be met by present-day active network techniques. The solution is found in the use of time-varying RC networks, i.e., by combining passive RC thin-film phase-shift networks with miniature transistors, used as electronic switches, in the form of so-called quadrature modulation circuits. The phase-shift networks, which in principle can be passive thin-film RC circuits, are in practice more easily realized as combinations of much simpler RC circuits with buffer amplifiers.     

Internal thermal feedback in four–poles especially in transistors

Thermal-electric interaction or "internal thermal feedback" occurs in temperature dependent devices and four-poles at low frequencies, if the thermal time constants are small. An electrical equivalent circuit which describes this thermal effect is generally derived and applied to transistors in common base and common emitter configuration. It consists of current sources and of resistance-inductance circuits which can be directly related to the thermal equivalent circuit of the device. It is shown that this thermal feedback should not be neglected in the measurement of high-frequency transistors, in the design of dc or video amplifiers and voltage or current regulators. Some measurements are reported and discussed. For instance, a strong frequency dependence of some four-pole parameters, especially of the forward trans-conductance y21and the short circuit output admittance y22eof high frequency transistors was found at frequencies below 1 Mc. These effects can be explained by the new equivalent circuit. Possible application of this thermal-electric interaction may include the realization of large low Q inductances for low frequency integrated circuitry, and perhaps the investigation of pinch-in and second breakdown effects. It appears that the low frequency noise figure of transistors may also be affected by this effect.     

Analytic investigation of frequency sensitivity in microwave oscillators: Application to the computation of phase noise in a dielectric resonator oscillator

The conversion of low frequency noise into phase noise in microwave oscillators is studied through an analytical calculation of the pushing factor. This calculation is based on a simplified equivalent circuit for two types of active devices : field effect transistors (Fet) and heterojunction bipolar transistors (hbt). The preeminence in the conversion process of the gate- source capacitance in theFet and the base- emitter junction in thehbt is pointed out. Practical methods are proposed to reduce the phase noise in these circuits.     

Transistor equivalent circuits

This paper surveys the history of the electric-circuit representation of the transistor over the past fifty years. During the first two decades after the transistor was announced in 1948, primary emphasis was on small-signal equivalent circuits, which could be used for linear-circuit analysis and design. In addition, parameters of many of these equivalent circuits for the bipolar junction transistor, which are described, were related to the physical construction of the device. Approximately two-thirds of the paper is devoted to this period, when the writer personally contributed to this effort. By the beginning of the third decade, transistor circuits had became more complex, and circuit analysis was carried out with the help of digital computers. Interest then shifted away from small-signal equivalent circuits to “models” for computer-aided circuit design (CACD). This transition, including the models used in the widely used CACD program SPICE, is described. MOS transistors are treated only briefly; by the time MOS transistors became commercially viable devices, emphasis then also had shifted to “models” for CACD. In conclusion, the writer notes that there is still hope for us aficionados of small-signal equivalent circuits; new types of transistors are still being characterized in this manner     

Modeling substrate effects in the design of high-speed Si-bipolarICs

In the design of high-speed IC's, the influence of the substrate on circuit performance must be considered carefully. Therefore, in this paper the contribution of the p^- substrate and channel stopper to the equivalent circuits of Si-bipolar transistors and bond pads are theoretically and experimentally investigated up to very high frequencies. Improved equivalent substrate circuits, well suited for standard circuit simulators (e,g., SPICE), are derived and checked by numerical simulation using a new simulator (called SUSI). The validity of both the numerical simulation results and the equivalent circuits are verified by on-wafer measurements up to 20 GHz. Finally, the simulator was successfully applied to investigate noise coupling via the substrate     

A flexible logic circuit based on a MOS-NDR transistor in standard CMOS technology

A MOS-NDR (negative differential resistance) transistor which is composed of four n-channel metaloxide-semiconductor field effect transistors (nMOSFETs) is fabricated in standard 0.35 μm CMOS technology.This device exhibits NDR similar to conventional NDR devices such as the compound material based RTD (resonant tunneling diode) in current-voltage characteristics.At the same time it can realize a modulation effect by the third terminal.Based on the MOS-NDR transistor,a flexible logic circuit is realized in this work,which can transfer from the NAND gate to the NOR gate by suitably changing the threshold voltage of the MOS-NDR transistor.It turns out that MOSNDR based circuits have the advantages of improved circuit compaction and reduced process complexity due to using the standard IC design and fabrication procedure.     

Zero-Voltage and Zero-Current Switching Full-Bridge DC–DC Converter With Auxiliary Transformer

A novel zero-voltage and zero-current switching (ZVZCS) full-bridge phase-shifted pulsewidth modulation (PWM) converter using insulated gate bipolar transistors (IGBTs) with auxiliary transformer is proposed to improve the properties of the previously presented converters. ZVZCS for all power switches is achieved for full load range from no-load to short circuit by adding active energy recovery snubber and auxiliary circuits. The principle of operation is explained and analyzed and experimental results are presented. The features and design considerations of the converter are verified on a 3-kW, 50-kHz IGBT based experimental circuit.     

Silicon npn bipolar transistors with indium-implanted base regions

In this paper, silicon npn bipolar transistors with indium-implanted base regions are discussed. Polysilicon emitter bipolar transistors are fabricated using a standard 0.5-μm BIC-MOS process flow where the base BF₂ implant is replaced by an indium implant. In indium-implanted transistors, the integrated hole concentration (G_b) in the quasi-neutral base is reduced due to incomplete ionization of indium acceptor states. The novel utilization of this impurity freeze-out effect results in much increased collector currents and common-emitter transistor gains (h_fe) compared to boron-implanted transistors. Also, since indium acceptor states in depletion regions become fully ionized, the spreading of the reverse-biased collector-base junction depletion region into the transistor base (base-width modulation) is minimized. Hence, for indium base bipolar transistor an improved h_fe-V_A product is anticipated. Our first attempt at fabricating bipolar transistors with indium-implanted base regions resulted in devices with greatly increased collector current, impressive gains of h_fe≈1600, excellent collector current saturation characteristics, an Early Voltage of V_A≈10 V, h_fe-V_A product of 16000 (implying an extended device design space), base-emitter breakdown voltages of BV_EBO≈9.6 V, and a cut-off frequency of f_t=17.8 GHz     

Note on unilateral power gain as applied to submicrometretransistors

A theoretical analysis of the unilateral power gain applied to submicrometre transistors for high-frequency performance is presented. The new exact formulas shows that one can distinguish three resonant conditions. The conclusions are based on analysis of two different equivalent circuits     

新型二阶磁控忆阻器简化模型的设计与验证

忆阻理论的提出极大地推进了混沌系统的发展,丰富了混沌电路的动力学行为。运算放大器因其强大的信号处理能力,成为忆阻器电路模型的重要组成部分。本文基于低功耗差分对构建了一种极简化的运算放大器,该运算放大器将所需晶体管数目减少至2个;以此运算放大器为基础,设计了新型二阶磁控忆阻器的模拟等效电路模型和硬件实验电路。结果表明：激励信号频率增加,斜“8”字形紧磁滞回线的旁瓣面积减小;激励信号幅度增加,斜“8”字形紧磁滞回线的旁瓣面积增加。电路仿真结果与硬件电路实验结果验证了新型磁控忆阻器模型的有效性与设计方法的正确性。     

Static and dynamic analysis of amorphous-silicon field-effect transistors

Analytical expressions have been developed for the analysis of static and dynamic behaviour of hydrogenated-amorphous-silicon based field-effect transistors. The current/voltage, capacitances and transcapacitances/voltage characteristics are related to the material parameters. The characteristic temperature, T_c, of the exponential band-tail states distribution is shown to influence strongly their shape and magnitude. An exact integration of the potential in the structure has allowed us to give expressions for the source and drain resistances. Finally, we present an equivalent circuit of a-Si:H TFT which can be employed in circuit simulation for the optimisation of integrated circuits.     

晶体管混合π型参数与Y参数的关系

晶体管高频小信号等效电路模型可用两种方法得到:一是把晶体管视为一个二端口网络,列出电流、电压方程式,拟定满足方程的网络模型,常采用Y参数模型;二是根据晶体管内部发生的物理过程来拟定的模型,即π型参数模型;同一个晶体管应用在不同场合可用不同的等效电路表示,同一晶体管的各种等效电路之间又应该是互相等效的,各等效电路中的参数可互相转换。     

Numerical Determination of Possible Multiple DC Solutions of Nonlinear Circuits

This paper proposes an approach to find possible multiple solutions of nonlinear resistive circuits. The approach does not guarantee to find all the solutions; its main features are efficiency, the ability to deal with circuits composed of elements described by the most common models employed in microelectronics, such as DIODEs, bipolar junction transistors, MOSFETs and the capability to simulate medium size circuits composed of, but not limited to, some thousand transistors. The proposed approach is based on the partitioning of the original circuit in subcircuits and on the construction of an oriented dependency graph that defines a suitable ordering in the solution of the subcircuits. The oriented dependency graph can have oriented loops and loops can be "sources" of multiple operating points. These loops can be opened by removing a minimal number of circuit nodes. In general these circuit nodes constitute a very small subset with respect to the nodes of the original circuit and as shown in the paper represent a peculiar aspect to search for multiple solutions of a nonlinear circuit.     

Dynamic-type CMOS four-valued logic circuits

We first briefly introduce the various kinds of basic CMOS four-valued logic circuit that can be suitably employed for circuits with clock pulses. Using these, the design of multiple-valued MAX and MIN circuits with many inputs, each of which has two quaternary figures, are developed. It is shown that the number of MOS transistors required for these circuits can be reduced in comparison to binary circuits having equivalent functions. Successful simulation results using SPICE-2 for the circuit operations are given.     

A New Extraction Technique for the Complete Small-Signal Equivalent-Circuit Model of InGaP/GaAs HBT Including Base Contact Impedance and AC Current Crowding Effect

In this paper, both ac current crowding and base contact impedance are considered and included in the T-type small-signal equivalent circuit of InGaP/GaAs heterojunction bipolar transistors. The ac current crowding effect and base contact impedance are modeled as a parallel$RC$circuit, respectively. Devices parameters of the equivalent circuit are obtained by a new parameters extraction technique. The technique is to directly analyze the two-port parameters of multibias conditions (cutoff-bias, open-collector, and active-bias modes). The parallel capacitances ($C_B$and$C_ bi$), base resistances ($R_B$and$R_ bi$), and base inductance$(L_B)$are especially determined under the active-bias mode without numerical optimization. In addition, the small-signal equivalent circuits of cutoff-bias and open-collector modes are directly derived from the active-bias mode circuit for consistency. By considering base contact impedance and intrinsic base impedance effects in the presented small-signal equivalent circuit, the calculated$S$-parameters agree well with the measured$S$-parameters. The observed difference in the slope for the unilateral power gain$(U)$versus frequency at high frequency is mainly attributed to the ac emitter current crowding effect and well modeled in this study.     

Transient analysis of junction transistors

The transient behavior of the surface barrier and diffused junction transistors may be represented by an equivalent network consisting of two diodes and a nonlinear base resistance. Expressions for the nonlinear resistance, the base-emitter voltage time response, and the collector current time response are derived and tested experimentally. The equivalent circuit allows us to predict hole storage time for direct-coupled transistor logic (DCTL) circuits.