Improving power conversion efficiency is an important goal in a world characterized by increasing energy demand. Indeed, in recent years, research has focused on overcoming the limitations of silicon devices to improve the performance of integrated electronic systems. Power systems with smaller size, higher switching frequency, and lower power consumption than existing products are in fact necessary to meet future market demands. In addition, portable devices are becoming smaller and lighter, making heat dissipation more difficult. In this framework, the topic of this chapter focuses on design solutions ranging from system in package to monolithic ones in the emerging gallium nitride technology, primarily conceived for power converters, such as adapters and chargers, where power density is a key parameter. Specifically, a high-performance gate driver is introduced together with its main building blocks (output buffer, comparator, and voltage regulators). The solution is designed, experimentally characterized, and compared with the prior art. It provides the highest output voltage (600 V) and power capability (3 kW), outperforming previously reported solutions.