what is the difference between ttl &cmos ic?

Answer 1

They are two different techniques for making digital logic components. These two are not the only digital logic technologies, although they are perhaps the most widely known. Other technologies include NMOS, ECL, and some others.

TTL stands for "transistor-transistor logic". It uses bipolar transistors. Bipolar transistors are constructed vertically into the surface of the semiconductor material (usually silicon). Each transistor has three regions that are in physical contact with one another. The regions are called emitter, base, and collector. All three regions are below the surface of the semiconductor.

CMOS stands for "complimentary metal oxide semiconductor". It uses MOS transistors. MOS transistors are constructed horizontally across the surface of the semiconductor materal. Each transistor has three regions, but they are not all in physical contact. The regions are called source, gate, and drain. The source and drain are below the surface, but the gate is constructed above the surface of the semiconductor material. The gate is separated from the semiconductor by a very thin layer of silicon dioxide (glass). Thus, the gate is electrically insulated from both the source and the drain. The gate exerts its effect on the device by means of its electric field, which can extend through the glass.