Interview Questions about Logic Gates

In this tutorial, we are going to learn about Logic Gates.

What are logic gates?

Answer – It is a physical device which performs logic operation on one or more logical inputs, and produces a single logical output.

How many types of logic gates?

Answer – All digital system can be constructed using basic gates. These gates have basic operation. Below are the common logic gates which are used in circuit.

  • OR gate
  • NOR gate
  • NOT gates
  • AND gate
  • X-OR Gate
  • NAND Gate
  • X-NOR Gate

Which are the basic Gates?

Answer –

  • OR gate
  • NOT gates
  • AND gate

Which are the arithmetic Gates?

Answer –

  • XOR gate
  • X-NOR gates

Which are universal logic gates?

Answer – Any logic gate can be constructed with the help of universal logic gates. Examples – NAND, NOR.

What is OR Gate?

Answer – The OR gate has two or more input signals but a single output signal. If any of the input signals is high the output signal is high.

Below is truth table for OR Gate.

InputsOutputs
ABY = A+B
000
011
101
111

What is NOR Gate?

Answer – A NOR gate has two or more input signals but only one output signal. It is combination of OR gate followed by NOT gate.

Below is the truth table for NOR gate.

InputsOutputs
ABY = A NOR B
001
010
100
110

What is NOT Gate?

Answer – NOT gate has only one input signal and one output signal. The output state is always the opposite of the input state. It is also called inverters.

Below is the truth table for NOT gate.

InputsOutputs
AY = NOT A
01
10

What is AND Gate?

Answer –An AND gate has two or more input signal and only one output signal. The output will be one only when both input are 1.

Below is truth table for AND Gate.

InputsOutputs
ABY = A+B
000
010
100
111

What is NAND Gate?

Answer –An NAND gate has two or more input signal and only one output signal. All input signals must be high to get low output. It is combination of AND gate followed by a NOT gate.

Below is truth table for NAND Gate.

InputsOutputs
ABY = A NAND B
000
010
100
111

What is X-OR Gate?

Answer – The exclusive OR gate gives high output when the inputs are not at equal logic level. The exclusive OR operation is widely used in digital circuit. It is called also XOR.

Below is truth table for X-OR Gate.

InputsOutputs
ABY = A B
000
011
101
110

What is X-NOR Gate?

Answer – The exclusive NOR gate gives 1 at output when the inputs are identical. It performs same function as XOR gate followed by a NOT gate.

Below is truth table for X-NOR Gate.

InputsOutputs
ABY = A XNOR B
001
010
100
111

What is Boolean algebra?

Answer – It’s the mathematical used in analyzing logic gates. With laws of Boolean algebra complex can be simplified.

 What is use of Logic gates?

Answer – in microprocessor, microcontrollers, digital circuit, embedded system, electrical projects, push button switches, alarms, safety thermostat etc.

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