Question

A logic gate which gives output 'HIGH' only when its two input terminals are at different logic levels with respect to each other is

• A. NOR gate
• B. OR gate
• C. AND gate
• D. X-OR gate

Hint:

Remember the names literally! "Exclusive-OR" means it functions like an OR gate but strictly excludes the case where both inputs are active together. It acts as an inequality detector or parity checker in digital electronics, producing a high output whenever the inputs disagree.

Answer 1

The Correct Option is D

Step 1: Understanding the Question:
The question asks us to identify a specific digital logic gate based on its operational truth behavior: it produces a logical high output ($1$) exclusively when its two input signals are completely distinct or mismatched (i.e., one input is $0$ and the other is $1$). 

Step 2: Key Formula or Approach: 
Review the behavior and boolean definitions of standard two-input logic gates: AND gate: Outputs $1$ only if both inputs are $1$ ($Y = A \cdot B$). OR gate: Outputs $1$ if at least one input is $1$ ($Y = A + B$). NOR gate: Outputs $1$ only if both inputs are $0$ ($Y = \overline{A + B}$). X-OR (Exclusive-OR) gate: Outputs $1$ if the inputs are strictly unequal ($Y = A\overline{B} + \overline{A}B$). 

Step 3: Detailed Explanation: 
Let's construct the complete operational truth table for an Exclusive-OR (X-OR) gate with inputs $A$ and $B$, and output $Y$:

Looking closely at the truth table, the output $Y$ is driven to a 'HIGH' level ($1$) if and only if the inputs are combinations $(0,1)$ or $(1,0)$. When the inputs share matching logic levels, such as $(0,0)$ or $(1,1)$, the output drops to a 'LOW' level ($0$). This matches the description in the prompt. 

Step 4: Final Answer: 
The logic gate described is the X-OR gate, corresponding to option (D).