This book focuses on the fundamentals of time-mode approaches and challenges encountered in the design of CMOS-based time-mode circuits. Building blocks of time-mode circuits such as voltage-to-time converters, time amplifiers, time registers, and time integrators are investigated. The design of time-to-digital and digital-to-time converters, the key building blocks of time-mode circuits, is covered as well as techniques that minimize the impact of nonlinearities in time-mode circuits. Time-mode analog-to-digital converters and time-mode phase-locked loops are emphasized in the book?s last section.