The output of an OR gate is connected to both the inputs of a NAND gate. The combination will serve as

  1. AND gate
  2. NOT gate
  3. NAND gate
  4. NOR gate

Answer (Detailed Solution Below)

Option 4 : NOR gate
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NDA 01/2025: English Subject Test
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Detailed Solution

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CONCEPT:

  • AND Gate: The Logic AND Gate is a digital logic circuit whose output is 1 (HIGH) only when all the inputs are 1 (HIGH)

F1 J.K Madhu 10.07.20 D12

A B C = A . B
0 0 0
0 1 0
1 0 0
1 1 1
  • OR Gate: The Logic OR Gate is a digital logic circuit whose output goes HIGH to a logic level 1 only when one or more of its inputs are HIGH

F1 J.K Madhu 10.07.20 D13  

A B C = A + B
0 0 0
0 1 1
1 0 1
1 1 1
  • NOT Gate: The Logic NOT Gate is the most basic of all the logic gates and is often referred to as an Inverting Buffer or simply an Inverter.

F1 J.K Madhu 10.07.20 D14

\(Y=\overline{A}\)

A B
0 1
1 0
  • NAND Gate: The logic Gate is obtained after adding NOT Gate after AND Gate.

\(Y=\overline{A.B}\)

  • NOR Gate: The logic Gate is obtained after adding NOT Gate after OR Gate.

\(Y=\overline{A+B}\)

F1 J.K 3.8.20 Pallavi D1.1

EXPLANATION:

F1 J.K 3.8.20 Pallavi D2

  • Since the output of OR Gate is input for both the inputs of NAND Gates, Both the inputs will be the same.
  • When a NAND gate is connected to the same input it acts as a NOT Gate.
  • The output of NAND Gate will be (same input)

\(Y=\overline{A.B}\)

\(Y=\overline{A.A}\)

\(Y=\overline{A}\)  (Same as NOT Gate)

  • If NOT Gate is added after OR Gate, It will act as NOR Gate.
  • So, The output of an OR gate is connected to both the inputs of a NAND gate. The combination will serve as NOR Gate. Hence the correct answer is option 4.
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