Modern digital logic ICs are widely available in three basic types: TTL devices (typified by the 74LS00 logic family), "slow" CMOS devices (typified by the "4000" logic family), and "fast" CMOS devices (typified by the 74HC00 and 74AC00 logic families). Each of these families has its own particular advantages and disadvantages, and its own special set of usage rules. This four-part mini-series explains the basic principles and usage rules of each of these three digital logic families, and provides practical usage guidance for the vast range of ICs available in each of these families. This opening article concentrates on digital logic IC basics.
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