ABSTRACT
Digital logic circuits can be classified as belonging to one of two categories, either combinational or sequential logic circuits. The integrated circuit switching logic used in modern digital systems generally comes from one of three families: transistor-transistor logic, complementary metal oxide semiconductor logic or emitter coupled logic (ECL). The transistor-transistor logic family has been the most widely used family type for applications employing small scale integration or medium scale integration integrated circuits. Digital circuits and systems operate in only two states, logic 1 and 0, usually represented by two different voltage levels, a high and a low. ECL is a nonsaturated logic family where saturation is avoided by operating the transistors in the common collector configuration. Latches and flip-flops are used to implement finite-state machines, counters and registers and are part of the configurable logic in complex programmable-logic devices and field programmable-gate arrays.
