As CMOS technology progresses rapidly toward the deep submicron regime, the integration level, performance, and fabrication cost increase tremendously. Thus, low-integration, low-performance small circuits or systems chips designed using deep submicron CMOS technology are not cost-effective. Only high-performance system chips that integrate CPU (central processing unit), DSP (digital signal processing) processors or multimedia processors, memories, logic circuits, analog circuits, etc. can afford the deep submicron technology. Such system chips are called system-on-a-chip (SOC) or system-onsilicon (SOS).1,2 A typical example of SOC chips is shown in Fig. 4.1.