Which of the following logic gate gives high output with all its inputs low
NOR
Logic Gate High Output All Low Inputs Explained
Logic gates are fundamental building blocks in digital electronics. They perform basic logical operations on one or more binary inputs to produce a single binary output. The output value is determined by the combination of input values according to a specific rule. Binary logic typically uses '0' (low or false) and '1' (high or true) to represent the two states.
This question asks us to identify the specific logic gate that outputs a 'high' signal (1) when all of its inputs are at a 'low' signal (0).
Analyzing Logic Gate Behavior
Let's examine the behavior of the common logic gates mentioned in the options when presented with all low inputs (e.g., inputs A=0 and B=0 for a two-input gate).
AND Gate Analysis
An AND gate outputs a high signal (1) only if ALL of its inputs are high (1). If any input is low (0), the output is low (0).
For inputs A=0, B=0, the AND gate output is 0 (Low).
OR Gate Analysis
An OR gate outputs a high signal (1) if ANY of its inputs are high (1). It only outputs a low signal (0) if ALL inputs are low (0).
For inputs A=0, B=0, the OR gate output is 0 (Low).
Ex OR (XOR) Gate Analysis
An XOR (Exclusive OR) gate outputs a high signal (1) if its inputs are DIFFERENT. If the inputs are the same (both low or both high), the output is low (0).
For inputs A=0, B=0, the XOR gate output is 0 (Low).
NOR Gate Analysis
A NOR gate is the inverse of an OR gate. It outputs a low signal (0) if ANY of its inputs are high (1). Conversely, it outputs a high signal (1) only when ALL of its inputs are low (0).
This behavior directly matches the condition stated in the question.
For inputs A=0, B=0, the NOR gate output is 1 (High).
We can illustrate this with a simple truth table for a two-input NOR gate:
| Input A | Input B | Output (A NOR B) |
|---|---|---|
| 0 (Low) | 0 (Low) | 1 (High) |
| 0 (Low) | 1 (High) | 0 (Low) |
| 1 (High) | 0 (Low) | 0 (Low) |
| 1 (High) | 1 (High) | 0 (Low) |
Conclusion: Identifying the Correct Logic Gate
Based on the analysis of the truth tables and the fundamental operations of each gate:
- AND, OR, and XOR gates all produce a low output (0) when their inputs are all low (0).
- The NOR gate is the only gate among the options that produces a high output (1) when all its inputs are low (0).
Therefore, the NOR gate is the correct answer.
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