Abstract:
The history of semiconductor devices starts in 1930’s when Lienfed and Heil first proposed the mosfet. However it took 30 years before this idea was applied to functioning devices to be used in practical applications, and up to the late 1980 this trend took a turn when MOS technology caught up and there was across over between bipolar and MOS share.CMOS was finding more wide spread use due to its low power dissipation, high packing density and simple design, such that by 1990 CMOS covered more than 90% of total MOS scale.
The concept of system-on-chip (SOC) has evolved as the number of gates available to a designer has increased and as CMOS technology has migrated from a minimum feature size of several microns to close to 0.1 µm. Over the last decade, the integration of analog circuit blocks is an increasingly common feature of SOC development, motivated by the desire to shrink the number of chips and passives on a PC board. This, in turn, reduces system size and cost and improves reliability by requiring fewer components to be mounted on a PC board.
Power dissipation of the system also improves with the elimination of the chip input- output (I/O) interconnect blocks. Superior matching and control of integrated components also allows for new circuit architectures to be used that cannot be attempted in multi-chip architectures. Driving PC board traces consume significant power, both in overcoming the larger capacitances on the PC board and through larger signal swings to overcome signal cross talk and noise on the PC board. Large-scale microcomputer systems with integrated peripherals, the complete digital processor of cellular phone, and the switching system for a wire- line data-communication system are some of the many applications of digital SOC systems.
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