Microelectronic Circuits, Fourth Edition is an extensive revision of the classic text by Adel S. Sedra and K. C. Smith. The primary objective of this text remains the development of the student's ability to analyze and design electronic circuits, both analog and digital, discrete and integrated. Fundamental developments in modern technology, particularly the increased emphasis on integrated circuits and the profusion of advances in digital electronics, require that engineers today be aptly equipped with knowledge of these concepts and techniques. In this edition, the authors present these concepts and techniques earlier on in the text and in greater detail than in previous editions. While the previous edition presented students with analog oriented concepts followed by digital, the fourth edition promotes learning these ideas side-by-side, as they often appear in the real world. Since most professors use Part 1 or the first 5 chapters of the text for a first course on basic devices, the new edition fully integrates the fundamental concepts of digital electronics into these critical chapters. The result is a clear and complete introduction to both the analog and digital concepts essential to building a solid foundation for a modern introductory course on electronic circuits. In order to help students fully comprehend the concepts presented, the amount of material in Part 1 on the physical operation of devices has been increased. Appreciation of these devices--how they are modeled using modern computer tools like SPICE, and the fact that most circuits designed today are integrated circuits--requires a firm grasp of device physics. To achieve this, the authors have increased the basic material on semiconductors and the PN Junction (Chapter 3), added additional material on Bipolar Junction Transistor operation (Chapter 4), and correspondingly increased coverage of MOSFET operation (Chapter 5). Instead of deliberately setting off this material into a separate chapter on device physics, the authors have integrated it into these chapters where appropriate. The result is a gradual introduction to these ideas within the context of their importance where they are needed. The material on digital electronics has been completely and thoroughly updated, expanded, and re-organized to reflect the tremendous advances in this area since the last edition. Since all electronics engineers need exposure to digital electronics early in their course work, a new section in Chapter 1 introduces the key element of digital electronics--the logic inverter--side by side with the fundamental element of analog electronics--the amplifier. This signifies the great importance of the emergence of digital electronics. More digital electronics has been added to Chapter 4 on the Bipolar Junction Transistor inverter as well as to a new section in Chapter 5 on the CMOS inverter. By including this expanded material early on in Part I, the student is exposed to the basics of analog and digital electronics in what is typically the first semester of the course (Part I, Chapters 1-5). MOS Digital Integrated Circuits (Chapter 13) has been completely rewritten and expanded to include more coverage of memory and an overview of digital circuit technologies, logic-circuit families and styles for digital system design. New topics have been added, including CMOS logic circuits and static and dynamic analysis, psuedo-NMOS logic, pass transistor logic, dynamic logic, dynamic techniques in flip-flop design, and ring oscillator. The MOSFET has become the most significant device in electronics today. The material on MOSFET (Chapter 5) has been entirely re-written to reflect the shift toward Integrated Circuit technology and the vast number of changes in MOS Integrated Circuit design. The amount of material devoted to JFET coverage has been substantially reduced. SPICE has been incorporated not only at the end of the appropriate device chapters (Chapters 3, 4, and 5), but also at the end of most chapters throughout the text, thereby increasing the flexibility to use this tool when desired. Emphasis is placed on models, when to use SPICE and what the benefits are. The placement of these SPICE SIMULATION EXAMPLES at the end of chapters allows the reader to use them optionally without interrupting the flow of the text. The authors have also included a short appendix on SPICE in the back of the book. For a complete introduction to SPICE, consult Roberts and Sedra's SPICE, Second Edition (0-19-510842-6). All examples are carefully chosen for their ability to illustrate the concepts of the chapter in a connected way. They demonstrate the power of SPICE and the potential advantages gained by using it. It should be carefully noted, however, that by-hand analysis is critical prior to employing SPICE. The Appendix on IC Fabrication has been thoroughly updated, and brief material on layout has been included. The hallmark end-of-chapter problem material has increased by offering nearly 30% more per chapter, providing well over 1300 homework problems. Many of the existing problems have been replaced or modified. See the ancillary information for additional problem material. Microelectronic Circuits, Fourth Edition, is intended for the core courses in electronic circuits taught to majors in electrical and computer engineering. All electrical and computer engineering students are required to take at least one semester of electronic circuits for which this text is intended. It should also prove useful to engineers and other professionals who wish to update their knowledge of fundamental electronic circuits. The text is supported extensively with ancillary materials.