A silicon integrated circuit (IC) is a compact functional electronic circuit that contains silicon-based semiconductors. Semiconductors have conductivity characteristics that can be controlled in various ways. The integrated circuit, also known as chip or microchip, is seen as a small component with terminals ranging from eight pins or more. Very large-scale integration ICs are used in computing devices that contain more than a million silicon transistors. Transistors are three-terminal devices that act as current-controlled current valves and are like electromagnetic relays, but with continuous current control instead of two-state or on/off control.
The semiconductor used in a silicon integrated circuit is the main entity referred to as a solid-state device. Before the first solid-state device was put into commercial use, the way to control the flow of electrons was to use a vacuum tube with a heater, cathode, plate, and at least a control grid. The size and power requirement of vacuum tubes now make them popular only in specialized fields such as extra-high power amplifiers for audio and radio applications. The silicon integrated circuit is very popular also due to the availability of silicon, as a common compound of silicon is found everywhere as ordinary sand. By proper heating in the absence of oxygen, semiconductor manufacturers are able to produce pure silicon, which can be further processed as diodes, transistors, and ICs.
The silicon integrated circuit is not used for radio signal applications because of the limitations of silicon semiconductor devices that are covered by the better signal performance of other semiconductors such as germanium semiconductors. In cell phones, the audio and alternating current (AC)/direct current (DC) power circuits use silicon semiconductor ICs. Computers and other digital devices make use of many silicon ICs. From the convenience outlet, the power supply uses silicon diodes capable of rectifying directly the main AC voltage. These diodes are usually in an encased switching power supply that employs silicon-based power regulator chips that are usually of the pulse-width modulation (PWM) type, which feedbacks the output DC levels as changes in the duty cycle of the power pulses.
Majority of the electronic circuits for relatively low-frequency applications use silicon-based semiconductors. The silicon diode is the most popular low-frequency power diode available in the market. Other switching semiconductors, such as the silicon-controlled rectifier (SCR), the three-terminal AC (TRIAC) device, and most audio power transistors, are made of silicon semiconductors. In solar photovoltaic panels, it is observed that silicon junctions that are exposed to sunlight produce an electrical potential across the terminals. This leads to the wide use of silicon-based solar panel devices that promise to become cheaper and cheaper as more research and manufacturing breakthroughs are achieved.