In recent years, there has been a trend to increase the switching frequency beyond multi-MHz in switching power converters to reduce the passive components and improve the power density significantly. However, this results in high-switching loss and gate-driver loss of the power MOSFETs. This book is about high-frequency power MOSFET gate driver technologies, including the gate drivers for the GaN HEMTs, which have great potential in the next generation switching-power converters. The gate drivers serve a critical role between the control and power devices. Although there are numerous research papers talking about the MOSFET gate drivers, there is actually no such a book focusing on the gate driver topic systematically. The contents mainly cover the state-of-the-art power MOSFET drive technique, the switching-loss model, current source gate drivers (CSDs), resonant gate drivers, adaptive gate drivers, and GaN HEMT gate drivers. The novel approach in this book is the proposed CSDs including different topologies, control, and applications. The CSD can reduce the switching-transition time and switching loss significantly, and recover high-frequency gate-driver loss compared to the conventional voltage gate drivers. The basic idea can also be extended to other power devices to improve high-frequency switching performance such as SiC MOSFET, IGBT, etc. It is expected that this book will be very useful to the design engineers in switching power supplies with various backgrounds. It can serve as a fundamental textbook to the undergraduates, graduates, and professionals in the power electronics field. We would like to thank our colleagues at Queen's Power Group. In particular, we would like to thank Wilson Eberle, Zhihua Yang, and Jizhen Fu for their contribution to the CSDs. We would also like to thank our graduate students in Nanjing University of Aeronautics and Astronautics, and they are Peng-Cheng Xu, Chuan-Gang Xu, Wei Cai, Jing-Ya Lin, Fei-Fei Li, Yuan Zhou, Zhou Dong, Zhi-Wei Xu, and Ke Xu.