- Analog chip
An "analog chip" is a set of miniature electronic
analog circuit s formed on a single piece ofsemiconductor material.The circuits in analog chips operate with
voltage and current varying in a continuous fashion; in contrast,digital chips only use and create voltages or currents at discrete levels, with no intermediate values. Analog chips often have passive elements (Inductor /Capacitor s/Resistor s) built into them, whereas most digital chips typically do not.Many modern analog chips contain digital logic elements also -- either to replace some analog functions, or to allow the chip to communicate with a
microprocessor . For this reason and since logic is commonly implemented usingCMOS technology, these chips useBiCMOS processes by companies such asFreescale ( [http://www.freescale.com/webapp/sps/site/overview.jsp?nodeId=014359sMjvtxRl&tid=taDR Freescale Analog products] ),Texas Instruments ,STMicroelectronics and others.The death of pure analog chips has been proclaimed regularly, however the field continues to grow and prosper. Some examples of long-lived and well-known analog chips are the 741
op-amp which was the original internally compensated opamp, and the 555 timer. The popular 555 timer was invented by Hans Camenzind in the 1970s.Power supply chips are also considered to be analog chips, but 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 ICsPMIC s are an important elements of those systems.Important basic building blocks of analog chip design include:
#current sources
#current mirror s
#differential amplifier
#bandgap references.All the above circuit building blocks can be implemented in bipolar as well as MOS technology. MOS Bandgap references use lateral (poor) bipolar transistors for their functioning.
People who have specialized in this field include
Bob Widlar ,Bob Pease ,Hans R. Camenzind ,George Erdi , andBarry Gilbert among others.References
*http://www.fairchildsemi.com/an/AN/AN-88.pdf
*http://www.fairchildsemi.com/an/AN/AN-118.pdf
*http://www.fairchildsemi.com/an/AN/AN-140.pdf
*http://www.fairchildsemi.com/an/AN/AN-340.pdfExternal links
* [http://www.arraydesign.com/ arraydesign.com The story of the design of the 555 timer]
* [http://www.designinganalogchips.com/ A free book called "Designing Analog Chips" is available for download from Hans Camenzind's site]
* [http://www.wisegeek.com/what-are-analog-chips.htm wiseGeek: What are Analog Chips?]
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