Logics or logic gates are the basic components of digital circuits. In the technical sense, logic means the linking ofdigital signals in terms of conjunction, disjunction, negation and antivalence according to the laws of Boolean algebra.
There are seven different basic logic gates: AND gates, OR gates, NOT gates, NAND gates, NOR gates, XOR gates and XNOR gates. These are technically realized by digital logic integrated circuits (ICs) in different technology and with different integration densities. In terms of circuit technology, logics can be based on diodes, transistors and resistors or on combinations of these components. They differ in the type of coupling within the logic. Known logic techniques are TTL logic, DTL logic, RTL logic, DRL logic, ECL logic, CML logic and DCTL logic.
Logics differ with regard to the level and polarity of the logic voltage and the supply voltage. A distinction is therefore made between positive and negative logic. The statement whether positive or negative logic always refers to the hi- or 1-level. With positive logic, the logic level for digital 1 is more positive than that of digital 0. The reverse is true for negative logic. The logic level depends on the logic and the technology. ECL log ics, for example, work with negative operating voltage and TTL logics with positive.