A linear integrated circuit or analog chip is a set of miniature electronic

analog circuit Analogue electronics ( en-US, analog electronics) are electronic systems with a continuously variable signal, in contrast to digital electronics where signals usually take only two levels. The term "analogue" describes the proportional rela ...

s formed on a single piece of

semiconductor A semiconductor is a material which has an electrical conductivity value falling between that of a conductor, such as copper, and an insulator, such as glass. Its resistivity falls as its temperature rises; metals behave in the opposite way. ...

material.

Description

The

voltage Voltage, also known as electric pressure, electric tension, or (electric) potential difference, is the difference in electric potential between two points. In a static electric field, it corresponds to the work needed per unit of charge t ...

and current 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 to

transistor upright=1.4, gate (G), body (B), source (S) and drain (D) terminals. The gate is separated from the body by an insulating layer (pink). A transistor is a semiconductor device used to Electronic amplifier, amplify or electronic switch, switch ...

s, analog chips often include a larger number of passive elements (

capacitor A capacitor is a device that stores electrical energy in an electric field by virtue of accumulating electric charges on two close surfaces insulated from each other. It is a passive electronic component with two terminals. The effect of a ...

resistor A resistor is a passive two-terminal electrical component that implements electrical resistance as a circuit element. In electronic circuits, resistors are used to reduce current flow, adjust signal levels, to divide voltages, bias activ ...

s, and

inductor An inductor, also called a coil, choke, or reactor, is a passive two-terminal electrical component that stores energy in a magnetic field when electric current flows through it. An inductor typically consists of an insulated wire wound into a ...

s) 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 as

gyrator A gyrator is a passive, linear, lossless, two-port electrical network element proposed in 1948 by Bernard D. H. Tellegen as a hypothetical fifth linear element after the resistor, capacitor, inductor and ideal transformer. Unlike the four con ...

s 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 a

microprocessor A microprocessor is a computer processor where the data processing logic and control is included on a single integrated circuit, or a small number of integrated circuits. The microprocessor contains the arithmetic, logic, and control circu ...

. For this reason, and since logic is commonly implemented using CMOS technology, these chips typically use BiCMOS processes, as implemented by companies such as Freescale,

Texas Instruments Texas Instruments Incorporated (TI) is an American technology company headquartered in Dallas, Texas, that designs and manufactures semiconductors and various integrated circuits, which it sells to electronics designers and manufacturers globa ...

STMicroelectronics STMicroelectronics N.V. commonly referred as ST or STMicro is a Dutch multinational corporation and technology company of French-Italian origin headquartered in Plan-les-Ouates near Geneva, Switzerland and listed on the French stock market. ST ...

, 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.Information Freescale website, Mar 28th 2010
About Freescale Analog Products
/ref> Purely analog chips in information processing have been mostly replaced with digital chips. Analog chips are still required for wideband signals, high-power applications, and

transducer A transducer is a device that converts energy from one form to another. Usually a transducer converts a signal in one form of energy to a signal in another. Transducers are often employed at the boundaries of automation, measurement, and cont ...

interfaces. Research and industry in this specialty continues to grow and prosper. Some examples of long-lived and well-known analog chips are the 741 operational amplifier, and the 555 timer IC.

Power supply A power supply is an electrical device that supplies electric power to an electrical load. The main purpose of a power supply is to convert electric current from a source to the correct voltage, current, and frequency to power the load. As a ...

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 circuit Power management integrated circuits (power management ICs or PMICs or PMU as unit) are integrated circuits for power management. Although PMIC refers to a wide range of chips (or modules in system-on-a-chip devices), most include several DC/DC ...

s, PMIC) are important elements of those systems. Important basic building blocks of analog chip design include: * current source * current mirror * differential amplifier * voltage reference, bandgap voltage reference All the above circuit building blocks can be implemented using bipolar technology as well as Metal-Oxide-Silicon (MOS) technology. MOS

band gap In solid-state physics, a band gap, also called an energy gap, is an energy range in a solid where no electronic states can exist. In graphs of the electronic band structure of solids, the band gap generally refers to the energy difference ( ...

references use lateral bipolar transistors for their functioning. People who have specialized in this field include Bob Widlar, Bob Pease, Hans Camenzind, George Erdi, Jim Williams, and Barrie Gilbert, among others.

References

Intelligent Power and Sensing TechnologiesCMOS Oscillators (AN-118)CMOS Schmitt Trigger—A Uniquely Versatile Design Component (AN-140)HCMOS Crystal Oscillators (AN-340)

Description

See also

References

Further reading