Test: Logic Gates & Switching Circuits- 1 - Electrical Engineering (EE) MCQ

• Positive logic AND gate is equivalent to bubbled NOR gate.
• Positive logic OR gate is equivalent to bubbled NAND gate.
• Positive logic NAND gate is equivalent to bubbled OR gate.
• Positive logic NOR gate is equivalent to bubbled AND gate.

 can be implemented using 4 NAND gates as shown below:

Thus, we see that after interchanging all 1’s and 0’s of inputs in the truth table of positive logic AND gate, the resulting truth table obtained is the truth table of negative logic OR gate. Similarly, we can prove that if all 0’s and 1's inputs in the truth table of NAND gate are interchanged, then the gate becomes negative logic NOR gate. Hence, both assertion and reason are true and reason is the correct explanation of assertion.

• EX-OR gate can be used as a controlled inverter as shown below:

For control input = 1 , 

For control input = 0, Y = A

• NOT gate is basically used as an inverter or for complementation purposes.
• EX-NOR gate can be used as even-odd parity checker because the output of EX- NOR gate is 1 if the number of 1’s in its inputs is even; if the number of 1’s is odd, the output is 0.
• NOR gate is an universal gate.

The solution to the assertion and reason question is as follows:

• The EX-NOR gate functions as a one-bit comparator because it outputs high when both its inputs are the same.

• The reason provided states that the EX-NOR gate outputs high if the number of high inputs is even and low if the number is odd. This is true but not why it works as a comparator.

• Therefore, both the assertion and reason are true, but the reason is not the correct explanation for the assertion.

Here, (0, 1, 1) gives the output X = 1

The numbers that differ by only a single bit from their preceding number are represented using the Gray code. Here is why Gray code is used:

• Gray code ensures that only one bit changes at a time, reducing the chance of errors during transitions.
• This property is important in systems where changes from one state to another should be smooth and error-free.
• Commonly used in rotary encoders and digital communication to ensure data integrity.

The AND gate follows both the commutative and associative laws. Here's why:

• The commutative law means that the order of inputs does not change the output. For an AND gate: A & B = B & A.
• The associative law allows grouping of inputs without affecting the result. For an AND gate: (A & B) & C = A & (B & C).

Therefore, the AND gate is the correct option as it satisfies both laws.

A latch is a type of digital storage device used to store one bit of data. It is a fundamental building block in digital electronics.

• Latches are commonly used in circuits to maintain a state until changed by an input signal.
• They differ from flip-flops, which are more complex and triggered by clock signals.
• A D-type latch holds a value with a single data input and a control signal.

Latches play a crucial role in memory devices and data storage operations in computing systems.