With fundamental questions such as "What is a complex frequency?", "What are negative resistances?", or "Can a signal propagation time be negative?", anyone who delves into circuits and systems for analog signal processing will eventually be confronted with these topics - whether as a student of information and communication technology or as an engineer in practice. This book answers 100 selected questions from the fields of system theory, amplifier and filter technology, as well as signal generation (oscillators), and addresses specific issues related to circuit simulation.