Qucs modelling and simulation of analog/RF devices and circuits (Chapter 6)

Trends in compact device modeling and analog circuit simulation point towards a growing interest among the modeling community in the standardization of Verilog-A as an equation based modeling language for compact semiconductor device model and circuit macromodel development. . This chapter introduces the principles of compact device modeling with equation-defined devices and VerilogA models. For completeness circuit macromodel principles and construction are also included. It also describes the use of the different types of equation based models in analog and RF circuit simulation. Throughout the text the properties of a range of analog and RF circuits with different levels of complexity are introduced and their performance investigated with the “Quite universal circuit simulator” (Qucs) and its related software package QucsStudio. All the device and circuit modeling techniques introduced in this chapter form part of the standard features implemented in Qucs and QucsStudio

Qucs-S help documentation release 0.0.21-S

Following the release of Qucs-0.0.18 in August 2014 the Qucs Development Team considered in detail a number of possible directions that future versions of the software could take. Spice4qucs is one of these routes. It addresses a number of problems observed with the current version of Qucs while attempting to combine some of the best features of other GPL circuit simulation packages. The project also aims to add additional model development tools to those currently available in Qucs-0.0.18. Qucs was originally written as an RF and microwave engineering design tool which provided features not found in SPICE, like S parameter simulation, two and multiport small signal AC circuit analysis and RF network synthesis. Since it was first release under the General Public License (GPL) in 2003 Qucs has provided users with a relatively stable, flexible and reasonably functional circuit simulation package which is particularly suited to high frequency circuit simulation. In the years following 2003 the Qucs Development team added a number of additional simulation facilities, including for example, transient simulation, device parameter sweep capabilities and single tone Harmonic Balance simulation, making Qucs functionality comparable to SPICE at low frequencies and significantly extended at high frequencies. Considerable effort has also been made to improve the device modelling tools distributed with Qucs. The recent versions of the software include code for algebraic equation manipulation, Equation-Defined Device (EDD) modelling, Radio Frequency Equation-Defined Device (RFEDD) simulation and Verilog-A synthesised model development plus a range of compact and behavioural device modelling and post simulation data analysis tools that have become central features in an open source software package of surprising power and utility. One of the most often requested new Qucs features is “better documentation”, especially documentation outlining the use and limitations of the simulation and the modelling features built into Qucs. Qucs is a large and complex package which is very flexible in the way that it can be used as a circuit design aid. Hence, however much documentation is written describing its functionality there are always likely be simulation and modelling examples that are missing from the Qucs documentation. In future Qucs releases will be accompanied by two or more basic Qucs documents. The first of these, simply called “Qucs-Help”, provides introductory information for beginners and indeed any other users, who require help in starting to use Qucs. The second Qucs document, called “Spice4qucs-Help”, introduces more advanced simulation and modelling topics. Both documents present a large number of typical circuit simulation and compact device modelling examples

A new offset cancellation technique for temperature sensors & Design of 8-bit decimation filter for biomedical applications

In our day to day life there are lot of things which we need to sense and then decide the course of action according to it. Many of these can be physically sensed easily, but the exact value of the sensed cannot be determined by human. There will be a lot of error in judged value and exact value. So instead of human sensing them and judging the exact value there are physical instruments which can provide lot more accurate value of sensed item than human, which are called SENSORS. There are lot of different sensors for sensing different things and one of prominent one is temperature sensor. Temperature sensor plays an important role in many applications. For example, maintaining a specific temperature is essential for equipment used to fabricate medical drugs, heat liquids or clean other equipment. For application like these, the accuracy of detection can be critical. The work done in this Thesis shows how to maintain the accuracy of temperature sensor. Temperature sensor used here is a Wheatstone bridge circuit consisting of two resistors and two thermistors. Mismatch between the resistors or thermistors will lead to incorrect detection of value, which is called OFFSET, therefore to maintain the accuracy the mismatch has to be minimized or removed. One of the Technique to minimize the offset and results pertaining to it has been displayed in this Thesis. Technique described in this Thesis consist of first sensing the difference between resistors value, one being the reference resistor and other the on-chip resistor used in temperature sensing, second amplifying the difference of resistor value using OPAMP, third sending the amplified signal to single ended SAR ADC, which gives digital bits as output. And according to the digital output changing resistor value using resistor switching method. Thus then this resistor will be used in wheat stone bridge temperature sensing. The work proposed here can increase or decrease on-chip resistor value depending on reference resistor. The wheat stone bridge Resistor can be changed by plus minus 5K ohms with respect to reference resistor. This is a onetime calibration technique used before start of sensing temperature. After the resistor have been calibrated, these resistors are used in wheat stone bridge along with thermistor to sense temperature and the differential output obtained through wheat stone is passed on to the dual ended SAR ADC, which gives digital representation of temperature sensed

Memristor Based Logic Circuits

The increased study of electronics has lead to breakthroughs that have allowed technology such has CMOS to create smaller and faster devices. However, this scaling has slowed down due to problems such as power dissipation. Technologies such as memory devices are unable to keep up with market demand for smaller and lower powered devices. A lot of different solutions have been proposed to solve this problem, one of which has been the use of memristors. The advantages of this technology are, no-volatility, good scalability, and compatibility with CMOS devices. Memristors can be used to improve existing technologies such as memory, logic and neuromorphic devices. This dissertation will focus first on the study of various memristor models, then the implementation of the various models studied will be addressed, then a single model will be chosen that better fits the requirements necessary to develop logic gates. Then, using the chosen model, more complex circuits will be implemented, first circuits composed of two memristors, then logic gates circuits

SPICE compact modeling of bipolar/unipolar memristor switching governed by electrical thresholds

In this work we propose a physical memristor/resistive switching device SPICE compact model, that is able to accurately fit both unipolar/bipolar devices settling to its current-voltage relationship. The proposed model is capable of reproducing essential device characteristics such as multilevel storage, temperature dependence, cycle/event handling and even the evolution of variability/parameter degradation with time.The developed compact model has been validated against two physical devices, fitting unipolar and bipolar switching. With no requirement of Verilog-A code, LTSpice and Spectre simulations reproduce distinctive phenomena such as the preforming state, voltage/cycle dependent<br/

Device Modelling of Silicon Based High-Performance Flexible Electronics

The area of flexible electronics is rapidly expanding and evolving. With applications requiring high speed and performance, ultra-thin silicon-based electronics has shown its prominence. However, the change in device response upon bending is a major concern. In absence of suitable analytical and design tool friendly model, the behavior under bent condition is hard to predict. This poses challenges to circuit designer working in the bendable electronics field, in laying out a design that can give a precise response in a stressed condition. This paper presents advances in this direction and investigates the effect of compressive and tensile stress on the performance of NMOS and PMOS transistor and a touch sensor comprising a transistor and piezoelectric capacitor

COMMON MODE VOLTAGE ELIMINATION IN THREE-PHASE FOUR-LEG INVERTERS UTILIZING PULSE DENSITY MODULATION

Common mode (CM) electromagnetic interference (EMI) is a phenomenon that negatively affects power electronics to include voltage source inverters. Typically, CM EMI reduction is achieved through passive measures such as CM chokes and passive filters. This thesis research explores removing the need for these passive devices in three-phase, four-leg grid-following inverters by eliminating CM EMI using pulse density modulation (PDM) in conjunction with model predictive control (MPC) and delta modulation. A physics-based model of the equipment under test (EUT), utilizing state-space modeling, was analyzed using computer simulations and a laboratory prototype, utilizing SiC switching devices, was designed to validate the model. The physics-based model of the proposed control system was converted to Verilog, a hardware description language (HDL) utilizing MATLAB HDL coder in order to control the laboratory prototype via a field-programmable gate array (FPGA). Simulated and experimental results demonstrate that both the unbalanced load requirements in MIL-STD-1399 and the conducted emission limits in MIL-STD-461G are met with the proposed controller, while the grid-following converter supplies a desired current to the load.Office of Naval Research, Arlington VA 22203-1995Outstanding ThesisLieutenant, United States NavyApproved for public release. Distribution is unlimited