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Question

_____ is the digital 2-input logic gate whose output is HIGH only when both its inputs are the same.

This question was previously asked in
RRB ALP 2018 CBT 2 Fitter Question Paper (21-Jan-2019) (Shift 3)
The correct answer is
EX NOR Gate

Logic Gate: Output High When Inputs Same

The question asks to identify a 2-input digital logic gate. The key condition is that its output is HIGH only when both inputs are the same.

Analyzing Logic Gate Functions

We need to find the gate whose output is logic 1 when its inputs are identical (both 0 or both 1). Let's examine the options:

  • EX OR Gate (XOR): Produces a HIGH output when inputs are *different*.
  • EX NOR Gate (XNOR): Produces a HIGH output when inputs are the same. This matches the required condition.
  • AND Gate: Produces a HIGH output only when *both* inputs are HIGH.
  • NAND Gate: Produces a LOW output only when *both* inputs are HIGH (inverse of AND).

Based on the functionality, the EX NOR gate is the correct answer.

EXNOR Gate Characteristics

The EXNOR (Exclusive NOR) gate, also known as the XNOR gate, implements logical equality. Its output is HIGH if and only if the inputs are equal.

The Boolean expression is:

Output = $A \odot B$

Or

Output = $\overline{A \oplus B}$

Where $A$ and $B$ represent the two inputs.

EXNOR Gate Truth Table

EXNOR Gate Truth Table
Input A Input B Output
0 0 1
0 1 0
1 0 0
1 1 1

The truth table confirms that the output is HIGH (1) exclusively when both inputs, A and B, are identical.

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Similar Questions

  1. In a logic circuit, two inputs A and B are applied to an AND gate, and the output of the AND gate is connected to the input of a NOT gate. If the inputs A and B are both at logic 0, what will be the output of the entire circuit?

  2. In a logic circuit, three SPST (Single Pole Single Throw) switches are used to implement a logic gate. The switches are connected in series. What is the output of the circuit if all switches are closed?

  3. _______ are universal logic gates.

  4. A three Input NOR gate gives high O/P when _____.
  5. The Output of NAND Gate is low in case ________

Important Questions from Logic Gates

  1. Which logical gate is included in a binary adder circuit to enable binary addition and subtraction?

  2. A Circuit that operates in such a way that its output is high only when all its inputs are high

  3. ______ is also known as Inverter.

  4. The minimum number of NAND gates required to reduce the expression ((A + B)C) D is:

  5. In which of the following gates, the output is high if and only if all inputs are high?

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