Digital integrated circuits are used to perform logical operations. Some examples of digital integrated circuits are logic gates, flip-flops, registers and counters. The basic building blocks of these circuits are NAND and NOR gates. Some important characteristics of digital integrated circuits are operating speed, power dissipation, logic flexibility, noise immunity, noise generation, availability of complex functions, supply voltage, operating temperature range, Fan-in/Fan-out and cost. Digital integrated circuits possess high operating speed. Operating speed is measured in terms of propagation delay and pair delay. Low power dissipation is a feature of Digital integrated circuits. Logic flexibility includes wired logic capability, availability of complement outputs, ability to drive other logic forms, I/O facilities, capability to drive nonstandard loads etc. Noise immunity is a great feature of Digital integrated circuits. Noise such as external noise, poer line noise, signal current noise, cross-talk noise, transmission line reflections etc. can be minimized by the techniques like appropriate circuit lay-out, shielding, grounding, decoupling, termination and matching. A complex function which is a grouping of basic gates in a single package is a special feature of Digital integrated circuits. Supply voltage should be of great standard and operating temperature range should be wide in Digital integrated circuits.