Digital circuits

In analog  circuits,  we think  something about  voltages on terminals ranging over natural values.  This provides us the freedom to make an enormous variety of digital circuits, but sometimes that freedom actually creates the design function  more difficult.  To developed ever more complex  digital circuits,  we may move to a much harder, digital abstraction, in which  the voltages on the ends are thought of as only taking on quantities that are either  "low"  or "high". This PCAP machine is build  up of a basis set of components, called gates, that are made out of simpler analog  circuit elements, such as resistors and transistors.  Adopting the  digital  abstraction is a big  limitation on the  types of circuits  that  can be created.   However, digital  circuits  may be easy to develop and  create  and  also can be inexpensive because  the basic components   are simple,  versatile,  and  combinations are easy to think  about.  These  characteristics allow  designers to create  incredibly complex  systems by designing small  parts  and  giving them  together into  increasingly larger pieces.  Digital calculators, watches, and computers are all developed this way.