Self Study: System on Chip

System on Chip(SoC) is a popular topic in chip design nowadays. SoC means combining digital and analog system on a single chip. Circuits used to build on a large board, now it can be packed on a tiny chip. The outcome, small multi-function devices such as cell phone and iPod.

Digital and analog system are often design separately. For digital system (e.g. CPU), CMOS technology is the favorite choice because it is cheap and consumes little power. For analog system (e.g. amplifiers, radio receivers), BJT, SiGe or GaAs technology are often employed because they have much better performance. CMOS, BJT, SiGe, GaAs are different semiconductor. Usually they can't be combined together so they are built separately.

As CPU becomes so popular, CMOS is now the dominate main-stream semiconductor. To reduce cost, companies are demanding designers to build both digital and analog system using only CMOS. Unfortunately, CMOS semiconductor naturally has weak analog performance. But the demand is there and money make people think. Designers gradually come up new ideas to build good analog circuits using CMOS. As a result people know better on packing both digital and analog system on a single chip based on CMOS. Maturity of SoC design should bring more creative portable electronics to the market.