# Digital Logic Interview Questions/Answers

In this article, we are going to see **basic** to **advanced Digital Logic Interview Questions** and **Answers**. **digital logic** basically deals with how we can represent the numerical value of quantities like analog and digital.

## Digital systems are the systems which

- deal with digital information in the external world
- use analog signals
- manipulate information
- handle information in digital form internally

**Answer – **(4) handle information in digital form internally

## Analog systems are different from digital systems because

- they use transistors
- they handle information in analog form
- they handle information in digital form
- they are slow

**Answer – **(2) they handle information in analog form

## Why are digital circuits easier to design than analog circuits?

- They do not control electricity precisely over a wide range.
- They are made in the form of ICs.
- All elements of digital circuits are from the same family.
- They are smaller in size.

**Answer – **(1) They do not control electricity precisely over a wide range

## A digital gate can respond to an input signal in

- about a second
- about a hundredth of a second
- a few billionths of a second
- a few milliseconds

**Answer – **(3) a few billionths of a second

## Analog methods are not used for handling extremely precise information because

- precise information always involves numbers which are inherently digital
- there are limits to how closely an analog signal can reproduce the information
- analog information never needs to be precise
- they are very expensive

**Answer – **(2) there are limits to how closely an analog signal can reproduce the information

## Which of the following is the first integrated logic family?

- RTL
- DTL
- TTL
- MOS

**Answer – **(1) RTL

## The time required for a pulse to change from 10 to 90 percent of its maximum value is defined as

- rise time
- decay time
- propagation tie
- operating speed

**Answer – **(1) rise time

## The main advantages of CMOS as compared to TTL are

- lower power consumption and better noise margins
- lower power consumption with low fanout
- higher speed operation with low power consumption
- higher power consumption with high fanout

**Answer – **(1) lower power consumption and better noise margins

## Standard TTL has a multiple-emitter input transistor and an output

- totem-pole
- chip
- bipolar
- loading-point

**Answer – **(1) totem-pole

## Which of the following boolean algebra statements represent distributive law

- (A + B) + C = A + (B + C)
- A . (B + C) = (A . B) + (A . C)
- A . (B . C) = (A . B) . C
- None of these

**Answer –** (2) A . (B + C) = (A . B) + (A . C)

## Which of the following boolean algebra statements represent commutative law

- (A + B) + C = A(B + C)
- A . (B + C) = (A . B) + (A . C)
- A + B = B + A
- A + A = A

**Answer – **(3) A + B = B + A

## Which of the following logic expression is incorrect?

- 1 ⊕ 0 = 1
- 1 ⊕ 1 ⊕ 0 = 1
- 1 ⊕ 1 ⊕ 1 = 1
- 1 ⊕ 1 = 0

**Answer – **(2) 1 ⊕ 1 ⊕ 0 = 1

## Let X and Y be the input and Z be the output of an AND gate. The value of Z is given by

- X + Y
- X . Y
- X . Y
- X . Y

**Answer – **(2) X . Y

## What logic gate is represented by the circuit shown below

- NAND
- NOR
- AND
- EQUIVALENCE

**Answer – **(3) AND

## The boolean expression A + BC equals

- (A + B) (A + C)
- (A + B) (A + C)
- (A + B) (A + C)
- none of these

**Answer – **(2) (A + B) (A + C)

## The clock signals are used in sequential logic circuits to

- tell the time of the day
- tell how much time has elapsed since the system was turned on
- carry serial data signals
- synchronize events in various parts of the system

**Answer – **(4) synchronize events in various parts of the system

## A positive AND gate is also a negative

- NAND gate
- NOR gate
- AND gate
- OR gate

**Answer – **(2) NOR gate

## The term product-of-sum in Boolean algebra means

- AND function of several OR functions
- OR function of several AND functions
- OR function of several OR functions
- AND function of several AND functions

**Answer – **(1) AND functions of several OR functions

## An n-stage ripple counter can count up to

- 2^n
- 2^n – 1
- n
- 2^(n-1)

**Answer – **(2) 2^n – 1

## A 2 MHZ signal is applied to the input of a J-K flip-flop which is operating in the toggle mode. the frequency of the signal at the output will be

- 1 MHZ
- 2 MHZ
- 4 MHZ
- 8 MHZ

**Answer – **(1) 1 MHZ

## Non-volatility is an important advantage of

- CCD’s
- RAM
- PROM
- EPROM

**Answer – **(3) PROM

**Note** – More questions and answers related to the interview will be added from time to time.