3 - Logic families

Abstract

Different electronic circuit configurations are available for the construction of logic circuits. A complete set of logic functions that use a common circuit configuration is known as a logic family. Many different logic families are available in integrated form, and those most commonly used are: (1) transistor-transistor logic (TTL), (2) complementary metal oxide semiconductor (CMOS), and (3) emitter-coupled logic (ECL). Logic families might be of the saturating or non-saturating type, and selection of a particular family depends upon the application being considered. The widely used type of saturating logic is transistor-transistor logic (TTL), which uses special multi-emitter transistors for its fabrication. A wide range of circuit functions from simple gates to complex counters and registers are available in the TTL family. Where low power consumption and compact assemblies are required, such as battery-operated portable equipment, a wide range of circuits are available that use CMOS construction. CMOS circuits are constructed from field effect transistors (FETs), using a mixture of n-channel and p-channel devices.