ESE 215
Introduction to Circuits and Systems

Prepared by: The Task Group on ESE 215-205

N. Farhat, N. Engheta, J. Keenan, and V. Vuchic

Background, Philosophy, and Motivation:

Over the past few decades, the scope of electrical engineering (ESE in the context of our department) has expanded to a degree where the discipline risks effacement by diffusion [1]. This calls for hard thinking on how to reform traditional course offerings in our discipline in order to avoid incoherent bifurcations forced from the outside and to preserve its identity in view of profound changes taking place. We are not alone. Similar reforms are being discussed in physics education [2]. We as a relatively newly formed department of Electrical and Systems Engineering have had a head start in thinking about this issue recognizing that the challenge is to forge something better than the sum of its parts. This draft proposal is an attempt at reforming the present introductory Circuits and Systems course in our curriculum in order to partly meet this challenge. We have changed the course title to indicate that it will deal with “circuits and systems” concepts in a broader sense than the traditional electrical circuits alone. Our goal is that the course encompass electrical, optical (plasmonic), mechanical, fluidic, biological, neural, transportation, chemical, and ecological “circuits” and systems.

Biochemical logic circuits using DNA-binding proteins, and bistable gene-regulatory networks acting as a toggle switch [5],[6] are being constructed. This gives an idea of the new types of elements future circuits and network would be built of. Similarly, plasmonic nano-optical components analogous to inductors, capacitors and resistance at optical frequencies being pioneered by researchers in our department, and Photonic Crystals will pave the way to plasmonic optical circuits, and the whole machinery of circuit theory can be brought to the optical domain. Other forms of circuits, such as chemical, fluidic, mechanical, neural, and transportation can also be envisioned

The term “system” used here and in the title refers to a collection of interconnected components or devices that act together to perform some specified objective or function and that every circuit, for example every electrical circuit, is a system but not every system is a circuit. For the systems engineer the term system has a broader connotation and methodology than in the context of circuits and systems [3]. The reformed course will also include, however, lectures on traffic and transportation circuits/networks that draw on the analogy between the flow (flux) of cars in such a network obeying the principle of conservation of mass and the flow of electrons in electrical and electronic circuits obeying the principle of conservation of charge. Extending the concept of flow to include sources, sinks and nonlinearity provides a means to treat the flow of traffic on a highway and pollutants in ecological systems [4] as well as preparing the student for flow of electrons and holes in semiconductor devices covered in subsequent courses.

All these indicate that the future circuit design will not be confined to electrical circuits alone. ESE students need to be made aware of this at an early stage of their curriculum. There is also little doubt that the complexity of DNA based, genetic-based, neural-based and other forms of circuits will exceed what is usually associated with electrical circuits. The course will therefore seek to provide an appreciation of complexity and its relation to nonlinearity.

In this course, some of the formal modeling and analysis techniques will be distilled from the material in (eq. [7], a possible text for the course), and covered in order to equip students with the necessary tools for analyzing general circuits. This will include giving formal modeling and analytical techniques of circuits obeying first order ODE and second order ODEs, linear circuits, Kirchhoff’s circuital laws, and network theorems with heavy reliance on worked-out numerical examples, computer simulations and class demonstration in order to enable devoting less class time to the drudgery of numerical manipulation and more to basic derivations, conceptual understanding, the meaning and use of theorems and applications and to pointing out the limitations of the techniques being discussed and how they relate to material in subsequent courses. Some of the saved time would be devoted to mechanical, optical (plasmonic), fluidic, chemical, and other forms of circuits and to the concepts of oscillations and resonance in an RLC circuit, the mechanical pendulum and the Belousov-Zhabotinski reaction that gives rise to chemical oscillations.

From sources (e.g., [8],[9],[10]) focusing on state-space and state equations and on interesting nonlinear devices and circuits, we will introduce students to the richness and added complexity resulting from nonlinearity. This will include biologically inspired model of the “integrate-and-fire” neuron which will lend a feeling of how biology realizes a spiking neuron employing ionic species rather than electrons used in electrical circuits. Accompanying lab exercises would include building and characterizing a physical integrate-and-fire circuit employing a programmable unijunction transistor or a glowlamp as the nonlinear element. The concept of frequency response and resonance in a nonlinear circuit and stochastic resonance phenomenon as compared to conventional resonance in a linear system can now be readily introduced.

We will then discuss a similar passage through a family of far more complex phenomena (such as ecological or transportation systems) for which few models exist that are both accurate and tractable. A possible source for this material is [4].

The semester would end with exercises and labs that assess the relevant models in relation to the mathematical and simulation tools, and strategies used to design with them. The laboratory exercises would be developed as collaborative group projects, and, where possible, with associated service learning modules.

References:

1. P. Wallich, Electrical Engineering’s Identity Crisis, IEEE Spectrum, pp. 67-71, Nov. 2004.

2. C. Wieman and K. Perkins, “Transforming Physics Education”, Physics Today, pp. 36-49, November 2005.

3. “What is Systems Engineering: A Concensus Opinion”, Compiled by T. Bahil, Source: Vucan Vuchic and Iraj Zandi.

4. E. Beltrami, Mathematics for Dynamic Modeling, Academic Press, Boston, (1987).

5. See for example: eeweb@princeton.edu, R. Weiss.

6. T. Gardner, C.R. Cantor and J.J. Collins, “Construction of a genetic toggle switch in Escherichia coli”, Nature, 403, pp. 339-342, January 2000.

7. J.D. Erwin and R.M. Nelms, Basic Engineering Circuit Analysis, John Wiley and Sons, (8th Edition), New York, (2005).

8. http://online.redwood.cc.ca.us/instruct/donald/deproj/sp98/Gabe. Also Google Belousov-Zhahotinski reaction for discussion and demonstrations.

9. http://www.colorado.edu/physics/phet/web-pages/simulations-base.html.

10. D.E. Scott, An Introduction to Circuit Analysis: A Systems Approach, McGraw Hill, New York (1987).