WHAT IS LOGIC GATES

Digital electronics is found in everything from computers to CD players and watches. It is based on the binary number system. Instead of voltages which vary continuously, as in analog electronics, digital circuits involve voltages which take one of only two possible values. In our case these are 0 and 5 volts (TTL logic), but they are often referred to as LOW and HIGH, or FALSE and TRUE, or as the binary digits 0 and 1.Basic building blocks of digital electronics are logic gates which perform simple binary logic functions (AND, OR, NOT, etc.). From these devices, one can construct more complex circuits to do arithmetic, act as memory elements, and so on. In this lab, you will look at a few basic devices to see what they can do. Logic gates and other digital components come in the form of integrated circuits (ICs) which consist of small semiconductor \chips packaged in a ceramic or plastic case with many pins. The ICs are labeled by numbers like 74LSxx, where xx is a number identifying the type of device.

NOT GATE (IC 7404)

In digital logic, an inverter or NOT gate is a logic gate which implements logical negation. The 7404 chip contains six inverters. An inverter simply converts binary 1 to 0 and vice versa.

AND GATE (IC 7408)

The AND gate is a digital logic gate that implements logical conjunction - it behaves according to the truth table to the right. A HIGH output (1) results only if both the inputs to the AND gate are HIGH (1). If neither or only one input to the AND gate is HIGH, a LOW output results. In another sense, the function of AND effectively finds the minimum between two binary digits, just as the OR function finds the maximum.

OR GATE (IC 7432)

The OR gate is a digital logic gate that implements logical disjunction - it behaves according to the truth table to the right. A HIGH output (1) results if one or both the inputs to the gate are HIGH (1). If neither input is HIGH, a LOW output (0) results. In another sense, the function of OR effectively finds the maximum between two binary digits, just as the complementary AND function finds the minimum

Exclusive OR Gate – EXOR Gate (IC 7486)

The EXOR gate is used extensively in digital data processing circuits and is known as Exclusive-OR-gate. The EXOR gate has a high output only when an odd number of inputs are high. For the two input EXOR gates, the output will be high when the set of input is either 01 or 10. The XOR gate is used in the adder, subtractor and controlled inverter circuit. It is also used in the computers for implementing the binary addition.