Digital Integrated Circuits

Abstract

Digital circuits form the great majority of integrated circuits manufactured today. There are many ranges available from various manufacturers and these tend to be classified by family type. They include Resistor Transistor Logic (RTL) of Fig.1, Transistor Transistor Logic (TTL) and Diode Transistor Logic (DTL) examples of which are shown in Figs.2 and 3, and Emitter Coupled Logic (ECL) shown in Fig.4. RTL was one of the earliest types to be introduced, but is now obsolete and rarely used in new designs. Both DTL and TTL are forms of Saturating Logic, so called because a transistor in the output stage saturates when the device operates. ECL is a form of Current Mode Logic which is nonsaturating and so achieves a faster switching speed. MOS transistors can be used with certain advantages in integrated circuits and these form a separate category.