Question

In the following digital circuit, what will be the output at ‘Z’, when the input $(A,B)are(1,0),(0,0),(1,1),(0,1):$

• A. $0,1,0,0$
• B. $1,1,0,1$
• C. $0,0,1,0$
• D. $1,0,1,1$

Answer 1

The correct option is C

$0,0,1,0$

Step 1: Define the all gates

Basic logic gates: There are seven basic logic gates: AND, OR, XOR, NOT, NAND, NOR, and XNOR.

The AND gate:

The following illustration and table show the circuit symbol and logic combinations for an AND gate. In the symbol, the input terminals are at the left and the output terminal is at the right. The output is "true" when both inputs are "true." Otherwise, the output is "false." In other words, the output is 1 only when both inputs one AND two are 1.

AND gate

Input 1	Input 2	Output
	1
1
1	1	1

OR gate: The output is "true" if either or both of the inputs are "true." If both inputs are "false," then the output is "false." In other words, for the output to be 1, at least input one OR two must be 1.

OR gate

Input 1	Input 2	Output
	1	1
1		1
1	1	1

The XOR: The output is "true" if either, but not both, of the inputs are "true." The output is "false" if both inputs are "false" or if both inputs are "true." Another way of looking at this circuit is to observe that the output is 1 if the inputs are different, but 0 if the inputs are the same.

XOR gate

Input 1	Input 2	Output
	1	1
1		1
1	1

NOT gate: A logical inverter, sometimes called a NOT gate to differentiate it from other types of electronic inverter devices, has only one input. It reverses the logic state. If the input is 1, then the output is 0. If the input is 0, then the output is 1.

Inverter or NOT gate

Input	Output
1
	1

The NAND gate: The NAND gate operates as an AND gate followed by a NOT gate. It acts in the manner of the logical operation "and" followed by negation. The output is "false" if both inputs are "true." Otherwise, the output is “true”.

NAND gate

Input 1	Input 2	Output
		1
	1	1
1		1
1	1

The NOR gate: The NOR gate is a combination OR gate followed by an inverter. Its output is "true" if both inputs are "false." Otherwise, the output is "false."

NOR gate

Input 1	Input 2	Output
		1
	1
1
1	1

The XNOR gate:

The XNOR (exclusive-NOR) gate is a combination XOR gate followed by an inverter. Its output is "true" if the inputs are the same, and "false" if the inputs are different.

XNOR gate

Input 1	Input 2	Output
		1
	1
1
1	1	1

Step 2: Calculate the output at ‘Z’

The truth table for the given circuit is shown below

Hence, the correct option is (C).