By Ian Darney

Back in the time when Circuit Theory was in its infancy, the existence of electromagnetic interference (EMI) was deemed to be of little significance. Engineering judgement at that time was that it could safely be ignored. Since then, the development of valves, transistors, integrated circuits and the Internet of Things has created a situation where ignoring EMI is no longer an option. But during this time, the fundamentals of Circuit Theory have remained unchanged.