An analysis of small-signal and large-signal base resistances forsubmicrometer BJT's

Small-signal and large-signal base resistances for submicrometer BJT's have been analyzed in detail by using a two-dimensional device simulator. It has been clarified that the small-signal base resistance cannot be obtained from the input impedance semicircle in the complex plane accurately due to the effect of the emitter resistance at low frequencies, and also due to the reduction of the base-emitter junction resistance and the diffusion capacitance at high frequencies. A new method for extracting an accurate value of the small-signal base resistance is proposed. The extracted small-signal base resistance not only differed from the large-signal base resistance extracted from the dc characteristics of a BJT, but also agreed with the differential resistance. It has been shown that, for a 0.6 μm emitter-width BJT, the measured value of the small-signal base resistance is less than half that of the large-signal base resistance in the bias region in which actual BJT circuits operate     

Low–frequency circuit theory of the double–base diode

The double-base diode is a single-junction semiconductor triode. When an electric potential is applied between the two ohmic contacts, a negative-resistance is obtained between the junction and one of the ohmic contacts. This negative resistance is bounded by two positive-resistance regions, one of considerably high magnitude which corresponds to the cut-off state and one of very low magnitude which corresponds to a saturating condition. The magnitude of the negative resistance is related to the ratio of majority-to-minority carrier mobilities. Small-signal low-frequency equivalent circuits are developed to approximate the double-base diode in each of the operating regions of the negative-resistance characteristic and equations for current and voltage amplification, input and output resistance and power gain are developed. The important circuit parameters are related to the physical constants of the device.     

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     

Impedance characterization of GaAs FET switches

Since the GaAs FET switch can be regarded as a linear small-signal device in the on and off states, a linear analysis is carried out only of the two states, but taking into account the geometry of electrodes, passivation layers, and depletion regions. The rectangular boundary division method is applied to solve Laplace's equation for the impedance characterization of GaAs FET switches. Equivalent electrical circuits composed of capacitors and resistors are defined for the on state and off state of a FET switch. The capacitances and resistances in the equivalent circuits are estimated and compared with experimentally measured values at 10 GHz. The quality factor of the FET switch, which can be used for estimating insertion loss, is calculated by using the two equivalent series impedances of the FET switch corresponding to the two states     

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     

Basic expressions and approximations in small-signal parameterextraction for HBT's

Basic expressions and approximations used to extract small-signal parameters for heterojunction bipolar transistors or bipolar junction transistors are developed in this paper. A T-type small-signal equivalent circuit after deembedding the pad capacitances is used for the derivation. The relative magnitudes of ωR_bcC_be , ωR_biC_bc, and ωr_cC _bell were used to evaluate the frequency ranges. Fully numerical or partially numerical approaches can be developed by these approximations. An element parameter-extraction procedure is also given in this paper. Two special cases (“cold” bias and degrading equivalent circuits) are also discussed     

Monolithic bipolar diodes and their models

The AC performance of the diode-connected, bipolar junction transistor (BJT) is examined. The discussion covers the BJT's most common connection, its small-signal behavior, and the current repeater that uses the diode as an input device. Looking at the AC behavior reveals the strengths and weaknesses of various models and simulators, primarily SPICE. It is shown that these common circuits are classic cases where models can fail     

考虑增益饱和及寄生参数的LD的模拟分析

基于包含增益饱和项的半导体激光器速率方程,分析了增益饱和因子和寄生参数对DFB激光器的动态特性的影响.建立了激光器用于数值计算的Simulink模型,对激光器的调制响应进行了数值分析;结合电子电路的特点,建立了一种考虑寄生参量的小信号等效电路模型,该模型将速率方程表征为由线性电路元件组成的电路模型;采用Matlab和PSpice两种软件模拟了该激光器的调制响应.结果表明张弛振荡频率和调制带宽随偏置电流的增加而增加,而增益饱和因子和寄生参数的存在使谐振频率衰减和带宽降低,同时也证明了所建模型的准确性和适用性.为改善DFB激光器的动态特性及优化设计器件结构参数提供了理论依据.     

Small-signal analysis of the phase-shifted PWM converter

The specific circuit effects in the phase-shifted PWM (PS-PWM) converter and their impact on the converter dynamics are analyzed. The small-signal model is derived incorporating the effects of phase-shift control and the utilization of transformer leakage inductance and power FET junction capacitances to achieve zero-voltage resonant switching. The differences in the dynamic characteristics of the PS-PWM converter and its PWM counterpart are explained. Model predictions are confirmed by experimental measurements     

Application of the distributed equilibrium equivalent circuit model to semiconductor junctions

The small-signal equivalent circuits for a p-n junction at equilibrium and the MOS capacitor in the inversion range are derived from the general transmission line model. Detailed calculations are made to obtain the semiconductor admittance as a function of frequency for a gold-doped n-type silicon substrate. The transmission-line model provides the desired distributed time constant observed in experimental data of admittance versus frequency. A simple model is given to illustrate how the low-frequency junction capacitance depends on the position of the deep level recombination center in the band gap and the ratio of the hole and electron emission rates. Experimental results on gold-doped silicon junctions are analyzed in terms of the theoretical model, considering effects of this ratio, the effects of surface channels, and the effect of a nonuniform spatial variation of the gold impurity.     

Frequency characteristics of a semiconductor rectifier at voltages greater than kT/q

In this paper, the frequency characteristics of a half-wave p-n junction rectifier with a resistance load are analyzed for applied voltages greater than kT/q. Beginning with the derivation of an implicit integral equation which describes the large-signal operation of this circuit, the effect of frequency on the rectification efficiency is then obtained from an iterative numerical solution of this equation using an IBM 650 computer. Contrary to the small-signal theory developed by Kalashnikov and Penin, it is found that at higher applied voltages the half-power frequency is very dependent on voltage as well as load resistance, carrier lifetime and reverse saturation current. The relationships between the half-power frequency and these parameters are shown graphically and the results are compared to the small-signal theory for small applied voltages.     

Negative resistance in p-n junctions under avalanche breakdown conditions, part II

The small-signal impedance of the space-charge region of p-n junctions under avalanche breakdown conditions is calculated using reasonably realistic dependences of electron and hole ionization rates and drift velocities upon electric field. Two structures are analyzed: one is p⁺νn⁺structure which has a fairly uniform distribution of avalanche multiplication, and the other is a singly diffused junction which is a hybrid of an abrupt and a linear graded junction. Both structures show negative resistance when the transit time of carriers becomes appreciable. A computer program was evolved which requires, as input, the impurity profile and field dependences of ionization rates and drift velocities. The program first calculates the dc field and electron and hole currents and then solves the ac small-signal problem. Both the ac small-signal impedance and theQof the diode are calculated.     

Efficient symbolic computation of approximated small-signalcharacteristics of analog integrated circuits

A symbolic analysis tool is presented that generates simplified symbolic expressions for the small-signal characteristics of large analog integrated circuits. The expressions are approximated while they are computed, so that only those terms are generated which remain in the final expression. This principle causes drastic savings in CPU time and memory, compared with previous symbolic analysis tools. In this way, the maximum size of circuits that can be analyzed, is largely increased. By taking into account a range for the value of a circuit parameter rather than one single number, the generated expressions are also more generally valid. Mismatch handling is explicitly taken into account in the algorithm. The capabilities of the new tool are illustrated with several experimental results     

压电陶瓷变压器在开关电源的应用分析

介绍了压电陶瓷变压器的原理,等效电路及特点。在此基础上,重点对应用压电陶瓷变压器的开关电源主电路,控制电路特点进行了分析,并简单介绍了压电陶瓷变压器目前在不同产品的开关电源中的实际应用。     

ANDREI-a minicomputer nonlinear analysis program for integrated circuits

A circuit analysis program, ANDREI, has been developed which can be run on a 32K 16-bit word minicomputer with a disk unit. A novel virtual storage scheme is used to save internal memory required by large arrays. The nonlinear DC and transient and small-signal AC analyses of circuits up to 150 nodes and 150 elements can be performed in the present version. Semiconductor device models for diodes, bipolar junction transistors, junction- and MOSFETs are built in. ANDREI runs presently on a 32K VARIAN 73 minicomputer.     

A wide–band square–law circuit element

A square-law circuit element with operating frequency range from zero into the vhf region is described. Its dynamic range and accuracy capabilities vary with the particular conditions under which it is operated; accuracies within less than one per cent of full scale and output dynamic ranges of over 100 db have been achieved. Frequency response limitations and possible sources of error are analyzed. Experimentally determined characteristics are presented and noise properties, dynamic range, and accuracy potentialities evaluated.     

Small-signal impedance of avalanching junctions with unequal electron and hole ionization rates and drift velocities

A small-signal analysis of an avalanching semiconductor junction is presented for unequal electron and hole ionization rates and saturated drift velocities. The model consists of a thin ionization layer in a thicker depletion layer. The ionization rates are assumed independent of distance in the ionization layer and zero elsewhere. This analysis is an improvement of Read's, and is sufficiently realistic to predict most of the small-signal characteristics shown by the computer analysis of Misawa. The linearized differential equations describing the ionization layer are solved with the ionization rates perturbed by the ac electric field. The ac junction impedance is calculated from the solutions of the differential equations. Although the small-signal analysis does not predict the conversion efficiency of an avalanche diode oscillator, it does predict the threshold conditions for oscillation. It may also help predict the conditions for maximum efficiency through knowledge of the input power and the Q of the diode at the onset of oscillation.     

Base-width modulation and the high-frequency equivalent circuit of junction transistors

The effect of base-width modulation on the exact small-signal, high-frequency equivalent circuit of p-n-p (and n-p-n) junction transistors is examined. It is found that (except for the effect on the base spreading resistance) base-width modulation only helps to determine the magnitude of one element. Failure to recognize this fact has resulted in the past in the "discovery" of "new" elements and the creation of a multiplicity of equivalent circuits. Through the use of an engineering approach, the most important of these circuits are related to the exact circuit, and hence their degree of approximation becomes apparent. The effect of a high injection level of minority carriers is also mentioned. Finally, the equivalent circuit of p-n-i-p (and n-p-i-n) transistors is discussed.     

Niobium-based integrated circuit technologies

Metallurgical and electrical properties of Nb and NbN films for use as Josephson junction electrodes and wiring layers are investigated. The crystallographic and superconducting properties necessary for Nb-based integrated circuit processes are clarified. Tunnel barrier structures of NbN-Nb oxide-NbN (Pb alloy) and Nb-Al oxide-Nb Josephson junctions have been analyzed and correlated with junction characteristics and critical current uniformity. It was found that the surface structure of a base electrode should be smooth to ensure that Josephson junctions have low leakage current and uniform critical current distribution. New types of Josephson junctions with artificial tunnel barriers such as amorphous Si or Mg oxide are reviewed. A variety of Josephson junction structures or processes have been developed for Nb-based Josephson integrated circuits in order to improve circuit performance. These include junction miniaturization, planarization, and stacked junction structures. These structures are mainly intended for Nb-Al oxide-Nb Josephson circuits. The Nb-Al oxide-Nb Josephson junction technology is by far the most advanced and has been used in logic and memory circuits, for example a 4-bit×4-bit parallel multiplier, a Josephson logic gate array, a 16-bit arithmetic logic unit, a 4-bit microprocessor, and 1-kb and 4-kb memory circuits     

Some properties and circuit applications of super–alpha composite transistors

A three-terminal amplifying device having the characteristics of a super-alpha Junction transistor can be constructed by making suitable interconnections between ordinary medium-alpha Junction transistors. It is shown that the circuit properties of such a device are very similar to those of a vacuum tube for many applications. Voltage-follower and voltage-amplifier circuits using composite transistors are described. Characteristics of two-stage and three-stage composite transistors are illustrated graphically.