ABSTRACT
VLSI technology has advanced so greatly that Gigabit DRAMs have become a reality, and the technology faces an optical lithography limit. Microelectronics mostly advances signal processing LSIs such as memories and microprocessors. Power systems and the related circuits cannot be outside the influence of VLSI technology.1 It would be quite strange for power systems alone to still continue to consume a large space while brains become smaller and smaller. On the other hand, almost all of the systems require actuators or power devices to control motors, displays, and multimedia equipment. The advances in microelectronics have made it possible to integrate large-scale circuits in a small silicon chip, ending up in high system performance and resultant system miniaturization. The system miniaturization inevitably necessitated power IC development. Typical early power ICs were audio power amplifiers, which used bipolar transistors as output devices. The pn junction isolation method was well suited to integrate bipolar transistors with control circuits.
