This is a compendium of practical wisdom concerning real world aspects of electronic circuit design gathered during years of experience in industry. The Companion enables circuit designers to produce more effective working circuits. Valued by linear and digital designers alike, this guide explains and outlines solutions that take into account the imperfect behaviour of real components, interconnections and circuits. Electronic circuit design can be divided into two areas: the first consists in designing a circuit that will fulfil its specified function; the second consists in designing the same circuit so that every production model of it will fulfil its specified function reliably over its lifetime. Designers who can appreciate the techniques and tools used in the latter area are becoming increasingly rare. The aim of this guide is to help such people. The subjects covered include grounding, printed circuit design and layout, the characteristics of practical active and passive components, cables, linear ICs, logic circuits and their interfaces, power supplies, electromagnetic compatibility, safety and thermal management. Throughout, the implications of manufacturability and cost are stressed. The style is direct and lucid, providing straightforward practical advice. This is the ideal guide to real world design for both students and practitioners.