A design theory for harmonic transistor oscillators

Imperial Users onl

Compact conversion and cyclostationary noise modelling of pn junction diodes in low-injection - Part I: Model derivation

Starting from the well known low-injection approximation, a closed form, analytical compact model is derived for the small-signal (SS) and forced quasi-periodic operation of junction diodes. The model determines the small-signal and conversion admittance matrix of the device as a function of the applied (dc or periodic-time varying) bias. Noise characteristics, in both the stationary (SS) and cyclostationary cases, are also evaluated by means of a Green's function approach

Design and analysis of fully integrated differential VCOs

Oscillators play a decisive role for electronic equipment in many fields-like communication, navigation or data processing. Especially oscillators are key building blocks in integrated transceivers for wired and wireless communication systems. In this context the study of fully integrated differential VCOs has received attention. In this paper we present an analytic analysis of the steady state oscillation of integrated differential VCOs which is based on a nonlinear model of the oscillator. The outcomes of this are design formulas for the amplitude as well as the stability of the oscillator which take the nonlinearity of the circuit into account. © 2005 Copernicus GmbH

Designers manual for circuit design by analog/digital techniques Final report

Manual for designing circuits by hybrid compute

A modified multiphase oscillator with improved phase noise performance

This paper investigates the factors that influence the phase noise performance of an oscillator and proposes a modified structure for improved phase noise performance. A single and multiphase oscillator analysis using the harmonic balance method is presented. The modified structure increases the oscillation amplitude without increasing the bias current and leads to improved phase noise performance as well as decreased power consumption. The modification is analyzed and the figure of merit of the oscillator shows a significant improvement of 21 dB. Numerical and analytical solutions are presented to predict the oscillation frequency and phase noise. The analytical solution is used to approximate the first harmonic and can be combined with numerical simulations to extrapolate phase noise performance.The measurements relating to this work were enabled through the support of SAAB Electronic Defence Systems (EDS). Funding was also received from the National Research Foundation (NRF), Department of Science and Technology, South Africa. NRF funding was for measurement equipment – a millimeter-wave vector network analyzer (under grant ID: 72321) and wafer-prober (under grant ID: 78580). NRF funding (under grant ID: 72321) also allowed collaboration with Prof Luca Larcher, Università degli studi di Modena e Reggio Emilia, Italy.http://www.elsevier.com/locate/mejo2018-04-30am2017Electrical, Electronic and Computer Engineerin

The mechanism of second breakdown in transistors

The purpose of this dissertation is to examine the behavior of electrons and holes in a semiconductor or diode under conditions of high current density as a function of temperature, and to relate this behavior to the phenomenon of Second Breakdown. The approach used is that of magnetohydrodynamics, the electrons and holes being treated as a plasma gas embedded in the dielectric of the semiconductor. This approach is unique in the following respects: This is the first attempt to explain second breakdown in terms of magnetohydrodynamics. This is the first time an explanation of pinching in a solid at room temperature has been presented which does not rely on some type of crystal imperfection to initiate the pinching. This is the first time variations in the forbidden gap width have been considered as causing voltage drops, and therefore, electric fields in a semiconductor. The author is convinced that there are really two types of second breakdown, depending upon the emitter bias. The first type of second breakdown occurs when the emitter-base junction is forward-biased, in which case current constrictions are due to pinching of electrons and holes in the base region of the device. This is examined in Part I of the dissertation, where the theory is developed for low electric fields. Computer calculations of electron-hole concentration and temperature versus distance from the hot-spot center are presented along with infrared data obtained for temperature versus distance for several measured hot spots. Agreement between theory and data is very good. The theory predicts that second breakdown is due to thermal effects at or near room temperature, and due to magnetic effects at or near liquid nitrogen temperature. This leads to the definition of the transition temperature as an indication of the temperature at which the transition occurs between second breakdown due to Joule heating, and second breakdown due to magnetic pinching. The most striking conclusion to be drawn from the computer results is that the theory predicts that units are much more susceptible to failure at lower temperatures than at higher temperatures, contrary to popular opinion. The second type of second breakdown occurs when the emitter-base junction is reverse-biased, in which case current constrictions are due to avalanche effects in the collector-base junction. This is examined in Part II of the dissertation, where the theory is developed for high electric fields. A critical current for the onset of second breakdown is determined as a function of electric field in the collector depletion region. Comparison of published data on the temperature dependence of second breakdown with theory is given first. Then data taken on a reverse-biased test set are presented. The temperatures investigated are 77°K, 195°K, 273°K, and 300°K. Theory predicts that devices are much more easily driven into second breakdown at low temperatures than at high temperatures, and this is verified experimentally. Experimental agreement with the theory is excellent over the entire temperature range investigated, in complete agreement with the theoretical results obtained in Part I. Actual devices will have flaws and defects in them, and will fail at power levels below their theoretical capabilities. This leads to the definition of a quality factor, which is a measure of the actual performance of a given device as compared to its theoretical capability

PLAWE: A piecewise linear circuit simulator using asymptotic waveform evaluation

Ankara : Department of Electrical and Electronics Engineering and the Institute of Engineering and Science of Bilkent University, 1994.Thesis (Ph.D.) -- Bilkent University, 1994.Includes bibliographical references leaves 73-81.A new circuit simulation program, PLAWE, is developed for the transient analysis of VLSI circuits. PLAWE uses Asymptotic Waveform Evaluation (AWE) technique, which is a new method to analyze linear(ized) circuits, and Piecewise Linear (PWL) approach for DC representation of nonlinear elements. AWE employs a form of Pade approximation rather than numerical integration techniques to approximate the response of linear(ized) circuits in either the time or the frequency domain. AWE is typically two or three orders of magnitude faster than traditional simulators in analyzing large linear circuits. However, it can handle only linear(ized) circuits, while the transient analysis problem is generally nonlinear due to the presence of nonlinear devices such as diodes, transistors, etc.. We have applied the AWE technique to the transient simulation of nonlinear circuits by using static PWL models for nonlinear elements. But, finding a good static PWL model which fits well to the actual i — v characteristics of a nonlinear device is not an easy task and in addition, static PWL modelling results in low accuracy. Therefore, we have developed a dynamic PWL modeling technique which uses SPICE models for nonlinear elements to enhance the accuracy of the simulation while preserving the efficiency gain obtained with AWE. Hence, there is no modelling problem and we can adjust the accuracy level by varying some parameters. If the required level of accuracy is increased, more simulation time is needed. Practical examples are given to illustrate the significant improvement in accuracy. For circuits containing especially weakly nonlinear devices, this method is typically at least one order of magnitude faster than HSPICE. A fast and convergent iteration method for piecewise-linear analysis of nonlinear resistive circuits is presented. Most of the existing algorithms are applicable only to a limited class of circuits. In general, they are either not convergent or too slow for large circuits. The new algorithm presented in this thesis is much more efficient than the existing ones and can be applied to any piecewise-linear circuit. It is based on the piecewise-linear version of the Newton-Raphson algorithm. As opposed to the NewtonRaphson method, the new algorithm is globally convergent from an arbitrary starting point. It is simple to understand and it can be easily programmed. Some numerical examples are given in order to demonstrate the effectiveness of the presented algorithm in terms of the amount of computation.Topçu, SatılmışPh.D