DIGITAL INTEGRATED CIRCUIT

Digital integrated circuits are those circuits,which perform logic function with the help of binary number 0 and 1;such as logic gates,flip-flops,counter,shift-registers etc.Digital ICs are most popular in realisation of electronic systems in the areas of instrumentation,communication,controls and computers.
In view of the low cost and excellent performance of digital ICs in silicon monolithic form,ICs based on monolithic technology are used nowadays.

Digital ICs,on the basis of technology involved in their manufacturing,can be classified into two categories namely bipolar and MOS (metal oxide semiconductor)families.The choice depends on the use of active devices in the circuit realisation. NPN  transistor is the most important devices in bipolar digital ICs and P- and N- channel MOSFETs with complementary symmetry circuitry are popular in MOS digital ICs.Thus the logic polarity of bipolar digital ICs is always positive whereas the logic polarity of MOS digital ICs is either positive or negative depending upon its configuration.
The NAND Or NOR logic gates are the universal building blocks in digital systems.So it is useful to compare the characteristics of NAND or NOR  gates employing different circuits configurations/active devices to characterize the different digital IC families. 

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