What is analog? This may seem like a strange question but the common understanding of analog has undergone a dramatic change in the digital era. Consider two definitions from the largest source of information today, a Google search.
Analog: the technology in use for more than 50 years to transmit conventional radio and TV signals. Vinyl recordings and motion picture films are examples of analog technology.
An analog (American English spelling) or analogue (British English spelling) signal is any continuously variable signal. It differs from a digital signal in that small fluctuations in the signal are meaningful. Analog is usually thought of in an electrical context, however mechanical, pneumatic, hydraulic, and other systems may also use analog signals.
Historically, analog IC technology was easy to identify. Chips that were op amps, low drop out regulators, drivers, and signal conditioning were definitely analog. Functions integrated in analog ICs included band gap reference, temperature sensing, voltage, and current limits thresholds. Today, integration combines many analog functions in digital ICs—especially the more complex system-on-a-chip ICs. Even traditional analog applications are increasingly part of the digital domain including digital control of motors and even power supplies.
Mixed signal technology is part of the transition in analog circuit technology that has occurred in the digital era. Frequently referred to as analog/mixed-signal technology, the design also has process implications.
Historically, analog ICs were designed using a bipolar IC process. Today, many analog ICs use the same or similar complementary metal-oxide semiconductor (CMOS) process as most digital ICs. Smart power technology is one of the more advanced semiconductor processing technologies in the analog IC arena. These designs combine bipolar, CMOS, and the double-diffused metal-oxide semiconductor (DMOS) processing used for power MOSFETs in a single, more complex process. Operating at voltage well above the traditional 5V or less used for digital ICs, smart power analog ICs integrate protection, diagnostic, other system functions, and typically handle amperes of current.
The analog ICs in this section pioneered more digital friendly and complete the system portions that are not integrated in the digital ICs.