Question

The inputs of a NAND gate are connected together. The resulting circuit is ___________

• A. OR gate
• B. AND gate
• C. NOT gate
• D. None of the above

Hint:

A NAND gate with both inputs connected together works as a NOT gate: \[ \overline{A\cdot A}=\overline{A} \]

Answer 1

The Correct Option is C

Concept:
A NAND gate is obtained by connecting an AND gate followed by a NOT gate. For two inputs \(A\) and \(B\), NAND output is: \[ Y=\overline{A\cdot B} \] If both inputs of NAND gate are connected together, then both inputs become the same. So: \[ A=B \]

Step 1: Write the NAND gate output.
For a NAND gate: \[ Y=\overline{A\cdot B} \]

Step 2: Connect both inputs together.
If both inputs are connected to the same signal \(A\), then: \[ B=A \] So: \[ Y=\overline{A\cdot A} \]

Step 3: Use Boolean algebra.
According to Boolean algebra: \[ A\cdot A=A \] Therefore: \[ Y=\overline{A} \]

Step 4: Identify the resulting gate.
The output: \[ Y=\overline{A} \] is exactly the output of a NOT gate. So NAND gate with tied inputs behaves as an inverter or NOT gate.

Step 5: Check the options.
Option (A) OR gate is incorrect.
Option (B) AND gate is incorrect.
Option (C) NOT gate is correct.
Option (D) None of the above is incorrect because option (C) is correct. Hence, the correct answer is: \[ \boxed{(C)\ \text{NOT gate}} \]