An analog semiconductor is an electronic component that supports many functions. It may either generate a signal or transform signal characteristics, such as amplitude, phase, and frequency. Analog semiconductors are categorized as low-power or high-power audio or radio frequency applications.
Analog semiconductors are widely used in power systems. The diode is a two-terminal semiconductor that converts or rectifies alternating current (AC) into direct current (DC). Various types of voltage regulators produce a clean DC without ripples and maintain an accurate DC voltage level. Without a voltage regulator, the power supply output voltage changes as DC load current changes. Power supplies that produce clean DC power are very important in home and professional equipment, such as entertainment systems, industrial equipment, and computers.
These semiconductors are also widely used for voice and music applications in audio systems. The common public address (PA) system is a series of audio amplifiers that accept a very small level of audio from a microphone and drive a speaker system. An audio preamplifier may accept a level of a few thousandths of a volt from a microphone then create a signal that is more than hundreds of times stronger in voltage and current, which is called amplification. Preamplifier stages are at the front end, while audio power amplifiers are in the final stages of audio system equipment. The analog semiconductor is usually used in all audio stages inside the PA system.
Wired voice communications also make use of an analog semiconductor. Traditional analog phones added new features, such as speakerphone or hands free, mute, transfer, and conferencing, which make use of the analog semiconductor in addition to digital counterparts. Wireless broadcast communications is implemented with analog semiconductors in numerous frequency bands and modulation types. In amplitude modulation (AM), the level or amplitude of the radio frequency (RF) carrier is controlled by the level of the voice or music on broadcast, while in frequency modulation (FM), the deviation level from the carrier frequency is controlled by the voice or music on broadcast. Television sets contain many analog semiconductors that process sound and video.
Automation systems use digital and analog technology. The traditional feedback control systems make use of the analog semiconductor to make better products and equipment that control such items as cars, elevators, and traffic lights. Analog circuits are usually referred to as linear devices, and the relationship of input to output of these devices may be described fairly accurately with a linear plot. Digital devices do not show a linear relationship of input to output levels. Instead, digital circuits use truth tables and sequential states at the logic level.