BE Lab Manual Experiment 1

Experiment 1

Aim: - To study AND gates, OR gates and NOT gates.

Apparatus: - Logic gate kit, patch chords.

Boolean Equations:-

(1)  Y = A.B (AND gate)

(2)  Y = A+B (OR gate)

(3)  Y = A or B (NOT gate)

Theory: - Logic gates are the fundamental building blocks of digital systems. The name logic gate is derived from the ability of such a device to make decisions, in the sense that it produces one output level when some conditions of input levels are present. Logic gates are electronics circuits because they are made up of a number of electronic devices and components of input variables and the corresponding output is called a truth table. There are three basic types of gates – AND, OR, NOT.

     (1)   The AND gate:-

 An AND gate has two or more inputs but only output. The output assumes the logic 1 state, only when each one of its inputs is at logic 1 state. The output assumes the logic 0 state even if one of its inputs is at logic 0 state. The AND gate may therefore one defined as a device whose output is 1, if and only if all its inputs are 1. The logic symbol and truth table of AND gate is shown in fig.  

Logic Symbol & Truth Table


(2) The OR gate:-

An OR gate has two or more inputs but only one output. The output assumes the logic 1 state, even if one of its inputs is in the logic 1 state. Its output assumes the logic 0 states, only which each one of its inputs is in logic 0 state. An OR gate may, therefore one defined as a device whose output is 1, even if one of its inputs is 1. The logic symbol and the table of the OR gate are shown in fig.

Logic Symbol & Truth Table

(3)   The NOT gate:-

 A NOT gate, also called an inverter, has only one input and, of course, only one output. It is a device that output is always the complement of its inputs. That is, the output of a NOT gate assumes the logic 1 state when its input is in logic 0 state and assumes the logic 0 states when its input 1 state. The logic symbol and the truth table of NOT gate are shown in fig.

Logic Symbol & Truth Table

Procedure:- 

  • For AND gate operation: - To operate AND gate, connect the logic input switch to the AND gate input shown in the figure and connect the output of AND gate to the logic indicator.
  • For OR gate operation: - To operate OR gate, connect the logic input switch to the OR gate input shown in the figure and connect the output of the OR gate to the logic indicator.
  • For NOT gate operation: -To operate NOT gate, connect logic input switch to the NOT gate input shown in the figure, and connect the output of NOT gate to the logic indicator.

 Observation Table:-

 (1)   For AND gate operation

 (2)   For OR gate operation

(3)   For NOT gate operation

 Result: - All the logic gates are verified.

 

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