Question

Which logic gate is represented by the following combination of logic gates ?

• A. NAND
• B. AND
• C. NOR
• D. OR

Answer 1

The Correct Option is B

The question asks which logic gate is represented by a specific combination of other logic gates. The correct answer given is "AND." Let's explore why the "AND" gate is the output of certain combinations of basic logic gates.

In digital electronics, basic logic gates exhibit simple truth table behavior which can be combined in specific ways to produce the behavior of other gates. Here's a breakdown:

1. NAND Gate: A NAND gate performs the opposite of an AND gate. The output of a NAND gate is true (1) when at least one of the inputs is false (0).
2. Using NAND gates to create an AND gate:
   • An AND gate can be formed by using two NAND gates in succession.
   • The first NAND gate negates the AND function, and the second NAND gate, used as an inverter (where both inputs are the same), negates the previous negation.
   • Thus, the combination of these gates results back in an AND gate.

Thus, combining two NAND gates as described will produce the output of an AND gate, which verifies that the correct answer is AND.

Let's briefly consider why the other options are incorrect:

• NAND: Provided by a single NAND and not a combination unless others invert the output.
• NOR: Requires specific configuration and inverting of a NOR output would not give an AND behavior.
• OR: In digital logic, creating an OR gate requires a different logic configuration that isn't derived from paired NAND gates directly.

Remember, logical equivalence derivation from basic gates is a foundational concept in digital circuits often encountered in exams focused on these topics.