180 Copyright © 2015, IGI Global. Copying or distributing in print or electronic forms without written permission of IGI Global is prohibited. INTRODUCTION Analog integrated circuit (IC) design using metal- oxide-semiconductor field-effect-transistors (MOSFETs) imposes challenges in sizing and selecting the right circuit topology (Tlelo-Cuautle 2011, 2013) because a huge plethora of active devices exist (Sánchez-López, Fernandez, Tlelo- Cuautle, & Tan, 2011; Sánchez-López, Martínez- Romero, & Tlelo-Cuautle, 2011). Each kind of active device provides different electrical charac- teristics, and then the same circuit under design may behave a little bit different using different active devices (Muñoz-Pacheco, Campos-Lopez, Chapter 8 Distributed Selection of the Optimal Sizes of Analog Unity Gain Cells by Fuzzy Set Intersection ABSTRACT A distributed system based on Fuzzy sets to select the optimal sizes of Unity Gain Cells (UGCs) is intro- duced. A zoom technique is also introduced to search for the optimal sizes in a more refned way. The selected sizes accomplish target specifcations established by linguistic variables, namely gain “closer to” unity and “large” bandwidth, which are represented by fuzzy sets. The case of study is focused on three Voltage Follower and a CFOA whose performance characteristics are evaluated by using IC technology of 0.35µm and 180µm, respectively, and the circuit simulation program SPICE. Every circuit is codifed by the width and large (W/L) of every Metal-Oxide-Semiconductor Field-Efect-Transistor (MOSFET) and by its bias current source. From the population of feasible solutions computed by evo- lutionary algorithms, the optimal W/L sizes are selected by the proposed distributed system through the intersection of fuzzy sets. Said Polanco-Martagón CENIDET, Mexico Gerardo Reyes Salgado CENIDET, Mexico Georgina Flores Becerra Instituto Tecnologico de Puebla, Mexico Esteban Tlelo Cuautle INAOE, Mexico DOI: 10.4018/978-1-4666-6627-6.ch008