Alinear integrated circuit oranalog chip is a set of miniature electronicanalog circuits formed on a single piece ofsemiconductor material.
Thevoltage andcurrent at specified points in the circuits of analog chips vary continuously over time. In contrast,digital chips only assign meaning to voltages or currents at discrete levels. In addition totransistors, analog chips often include a larger number of passive elements (capacitors,resistors, andinductors) than digital chips. Inductors tend to be avoided because of their large physical size, and difficulties incorporating them into monolithic semiconductor ICs. Certain circuits such asgyrators can often act as equivalents of inductors, while constructed only from transistors and capacitors.
Analog chips may also contain digital logic elements to replace some analog functions, or to allow the chip to communicate with amicroprocessor. For this reason, and since logic is commonly implemented usingCMOS technology, these chips typically useBiCMOS processes, as implemented by companies such asFreescale,Texas Instruments,STMicroelectronics, and others. This is known as "mixed signal processing", and allows a designer to incorporate more functions into a single chip. Some of the benefits of this mixed technology include load protection, reduced parts count, and higher reliability.[1]
Purely analog chips in information processing have been mostly replaced with digital chips. Analog chips are still required for wideband signals, high-power applications, andtransducer interfaces. Research and industry in this specialty continues to grow and prosper. Some examples of long-lived and well-known analog chips are the741 operational amplifier, and the555 timer IC.
Power supply chips are also considered to be analog chips. Their main purpose is to produce a well-regulated output voltage supply for other chips in the system. Since all electronic systems require electrical power, power supply ICs (power management integrated circuits, PMIC) are important elements of those systems.
Important basic building blocks of analog chip design include:
All the above circuit building blocks can be implemented using bipolar technology as well as metal-oxide-silicon (MOS) technology. MOSband gap references use lateral bipolar transistors for their functioning.
People who have specialized in this field includeBob Widlar,Bob Pease,Hans Camenzind,George Erdi,Jim Williams, andBarrie Gilbert, among others.