Author: Roberto Castañeda Sheissa

CAD tool for amplifier design on negative-feedback nullor based ampliers

ROBERTO CASTAÑEDA SHEISSA (2007)

Traditional circuit design has as starting point a similar already proved design that could

accomplish the desired specs. Once the circuit is selected, modifications are performed within

it in order to provide the required performance. Unfortunately, this way to perform circuit

design has several drawbacks, among them there are two such as:

• The time needed to perform the adaptation of the circuit is too high.

• Given the case that there is no circuit that could be adapted, it is necessary to invest

valuable time and resources to create a new one.

This thesis presents the design and development of an automated tool aimed at the

design of negative feedback amplifiers based on the Structured Circuit Design theory. The

main idea of this methodology is to establish an ideal solution first and from this starting

point, perform the required modifications to find the particular solution of the problem. The

base element of this methodology is the nullor, which is an ideal two-port element with these

important characteristics:

• The voltage and current at the input port always are zero.

• At the output port, the voltage and current values will always accomplish the load

requirements.

This methodology allows to create amplifiers with one or two feedback loops and the

topologies that can be implemented are: voltage amplifier, transconductance amplifier, transimpedance

amplifier and current amplifier.

To reach the implementation of the amplifier is necessary, at first instance, to perform

the nullor synthesis. The synthesis is performed by means of active devices since they are

the only ones capable to emulate the nullor characteristics. Nevertheless, the active devices

have some limitations like: noise generation, limited operational frequency or a narrow bias

range. The active devices in this work have been modelled using their small signal models,

this way is possible to depict any active device using just capacitors, resistors and controlled

sources. Using the small signal models are valid through the design process because the main

goal is to obtain a Butterworth like output, accomplish certain noise level and the output

signal are kept within certain voltage or current level. Therefore, the main focus of this work

lies in the AC domain while the DC bias values will be taken into account just in certain

design aspects.

El diseño tradicional de circuitos utiliza como punto de partida un circuito con características

similares a las que se desea cumplir. Una vez seleccionado el circuito, se modifica de tal manera

que cumpla las condiciones de operación para el nuevo diseño. Desafortunadamente esta

manera de diseñar circuitos electrónicos tiene varios inconvenientes, los dos mas importantes

son:

• El tiempo que se invierte en adaptar el circuito a las nuevas condiciones de operación

es muy alto.

• En caso de que no exista un diseño que se pueda adaptar, es necesario invertir tiempo

y recursos para crear uno nuevo.

Este trabajo de tesis presenta el desarrollo e implementación de una herramienta para

automatizar el proceso de diseño de amplificadores con retroalimentación negativa basado

en la teoría de Diseño Estructurado de Circuitos. El fundamento principal de esta teoría

es establecer una solución ideal y, a partir de esta, se procede a realizar las modificaciones

necesarias para poder llegar a la solución particular del problema. El elemento base que

utiliza esta metodología es el nullor, el cual es un elemento ideal de dos puertos con las

siguientes características principales:

• En el puerto de entrada el voltaje y la corriente tienen valor de cero.

• El puerto de salida tiene valores de voltaje y corriente que siempre cumplen los requerimientos

de la carga.

En este trabajo, los amplificadores a realizar serán aquellos con con uno y dos lazos de

retroalimentación. Las topologías que se pueden implementar son: amplificador de voltaje,

amplificador de transconductancia, amplificador de transimpedancia y amplificador de corriente.

Debido a que el nullor es un elemento ideal, es necesario realizar la síntesis de este

dispositivo utilizando elementos “reales” tales como resistencias, capacitores, transistores,

etc. La síntesis se lleva a cabo por medio de dispositivos activos, ya que son los únicos que

pueden, hasta cierto punto, recrear las características de amplificación que posee el nullor.

Sin embargo, los dispositivos activos tienen ciertas limitantes como lo son: generación de

ruido, frecuencia de operación limitada o un rango estrecho de valores de alimentación.

Los dispositivos activos en este trabajo se han modelado utilizando sus modelos de pequeña

señal, es decir, el dispositivo activo se representa utilizando elementos capacitivos, resistivos

y fuentes controladas.

Doctoral thesis

Computer aided engineering Amplifiers Analogue circuits CIENCIAS FÍSICO MATEMÁTICAS Y CIENCIAS DE LA TIERRA FÍSICA ELECTRÓNICA DISEÑO DE CIRCUITOS

Homotopy method with a formal stop criterion applied to circuit simulation

Héctor Vázquez Leal Luis Hernández Martínez Librado Arturo Sarmiento Reyes Roberto Castañeda Sheissa AGUSTIN GALLARDO DEL ANGEL (2011)

The continuous scaling for fabrication technologies of electronic circuits demands the design of new and improved simulation techniques for integrated circuits. Therefore, this work shows a new double bounded polynomial homotopy based on a polynomial formulation with four solution lines separated by a fixed distance. The new homotopy scheme presents a bounding between the two internal solution lines and the symmetry axis, which allows to establish a stop criterion for the simulation in DC. Besides, the initial and final points on this new double bounded homotopy can be set arbitrarily. Finally, mathematical properties for the new homotopy are introduced and exemplified using a benchmark circuit.

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Héctor Vázquez Leal Roberto Castañeda Sheissa CARMEN GUILLERMINA BLAZQUEZ DOMINGUEZ Luis Hernández Martínez (2011)

The health system for any country is one of the top priorities to guarantee the proper development for their citizens. For the specific case of Mexico, management of medical records is still being done using physical files whether patient attends a public or private physician or hospital. This poses a potential problem for the health structure and the patient because physical files tend to deteriorate, damage, could be stolen or mishandled. One possibility is to evolve from the use of physical files and create electronic medical records. Mexico already has an official standard for medical records; this standard could serve as the foundation to devise an electronic universal record. The idea for the electronic universal record is to serve as the base to implement an electronic public health scheme. This article will provide several key aspects to take into account in order to provide an efficient, secure and cost efficient electronic medical record. Aspects to be considered include: standardized medical nomenclature, clinical procedures, data transmission standards, legal aspects, electronic security, and data storage schemes. The impact of this proposal for Mexico will be discussed in detail.

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A handy, accurate, invertible and integrable expression for Dawson’s function

Una expresión compacta y precisa además de invertible e integrable de la función de Dawson

URIEL ANTONIO FILOBELLO NIÑO Héctor Vázquez Leal AGUSTIN LEOBARDO HERRERA MAY ROBERO CARLOS AMBROSIO LAZARO Roberto Castañeda Sheissa (2019)

En este artículo se propone una expresión compacta y precisa de la función de Dawson, la cual es invertible e integrable. Se observa que el error relativo máximo que se encuentra empleando la aproximación aquí propuesta es del 2.5%. Por consiguiente, se hace notar que la aproximación a la integral de la función de Dawson, que se expresa solo en términos de funciones elementales, tiene un error absoluto máximo de 7 × 10-3. A manera de ejemplo, se aplicará la aproximación aquí propuesta a un problema no-clásico de conducción de calor para obtener una solución aproximada, compacta y precisa

This article proposes a handy, accurate, invertible and integrable expression for Dawson’s function. It can be observed that the biggest relative error committed, employing the proposed approximation here, is about 2.5%. Therefore, it is noted that this integral approximation to Dawson’sfunction, expressed only in terms of elementary functions, has a maximum absolute error of just 7 × 10-3. As a case study, the integral approximation proposed here will be applied to a nonclassical heat conduction problem, contributing to obtain a handy, accurate, analytical approximate solution for that problem

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Powering multiparameter homotopy-based simulation with a fast path-following technique

Héctor Vázquez Leal Roberto Castañeda Sheissa FELIPE DE JESUS RABAGO BERNAL Luis Hernández Martínez Librado Arturo Sarmiento Reyes URIEL ANTONIO FILOBELLO NIÑO (2011)

The continuous scaling for fabrication technologies of electronic circuits demands the design of new and improved simulation techniques for integrated circuits. Therefore, this work shows how the hypersphere technique can be adapted and applied to trace a multiparameter homotopy. Besides, we present a path-following technique based on circles (evolved from hypersphere), which is faster, and simpler to be implemented than hypersphere technique. Last, a comparative analysis between both techniques applied to simulation of circuits with bipolar transistors will be shown.

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