Basics

Construction of Basic Logic Gates using NOR Gate

Logic gates are basically are group of three basic logic gates specifically called as NOT , AND and OR gate. All the Basic Logic Gates using NOR logical function. By the combination of these gates, we can obtain any Boolean or logical functions or logical function.

Outline

• Truth Tables of Basic Logic Gates:
• 1. NOT Gate:
• 2. AND Gate:
• 3. OR Gate:
• 4. NOR Gate:
• Transformation of NOR Gate into Basic Logic Gates:
• 1. Construction of NOT Gate using NOR Gate:
• 2. Construction of OR Gate using NOR Gate:
• 3. Construction of AND Gate using NOR Gate:

Truth Tables of Basic Logic Gates:

We first need to get aware with the working of each and every gate before knowing the conversion.

1. NOT Gate:

It is the simplest form of digital logical circuit. These using have two terminals, one for the input and the other for the output, and the input to the NOT gate can only be a binary number, i.e. it can be a 0 or a 1. The NOR gate’s output is always the inverse of the input, which means that if we place logic 1 at the gate’s input, the output will be logic 0 and vice versa. 2n (where n is the number of input) can be used to compute the number of stages that can be obtained. Because we only have one input in these cases, the number of stages that can be obtained is either 0 or 1. (21).

Truth table of NOT gate is shown below-

2. AND Gate:

The AND gate is a three-terminal device that has two input terminals and one output terminal. The logic gate operates in such a way that the output is binary 1 if and only if both inputs are binary 1. If any of the inputs are in the binary 0 state, the output will be binary 0 as well. A gate truth table can be found below.

The maximum number of stages that can be obtained is 2n (n is the number of the input terminals)

So, 2= 22  = 4.

3. OR Gate:

OR gate, like AND gate, is a fundamental logic gate with two inputs and one output. The operation of the gate is such that if any of the inputs is binary low, the output is binary 1, and we only get logic zero if both inputs are low. The OR gate truth table is as follows:

Number of possible stages = 2n =22 = 4.

4. NOR Gate:

The term NOR gate refers to a combination of the NOT and OR gates. As a result, a NOR gate is made up of an OR gate followed by an inverter. If all of the inputs are in the binary low state, i.e. 0, the output will be in the binary high state, i.e. 1, and if any of the inputs are in the binary high state, the output will be binary low.

The NOR’s phrase as well as truth table are presented below –

1. Construction of NOT Gate using NOR Gate:

Because the NOT gate only has one input, both input terminals have been shorted, as can be seen in the diagram above. When we supply a binary high signal, such as 1, at the input, the output will be binary low, such as 0, as you can see from the NOR gate’s truth table. We used the IC 7402, which is a quad two-input NOR gate.

3. Construction of AND Gate using NOR Gate:

or getting familiar with these it is important that one should have knowledge about the De Morgan’s theorem – According to the theorem the sum of the complement is equal to the product of the complement.

(A+B)‾ = A‾ . B‾                 –       EQ 1

From the figure shown above, Two NOR gate is been used by us and we short the input terminal of each gate so the output we will obtain as

= A‾ + B‾

Now  these output is again given as an input of the another NOR gate and the output which we will get as

= (A‾ + B‾)‾

=A‾ ‾ + B‾ ‾

= A.B

Required Components:

• IC
• CD7402 – 1
• R1 (1K) – 1
• LED – 1

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