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

1. deal with digital information in the external world
2. use analog signals
3. manipulate information
4. handle information in digital form internally

Answer – (4) handle information in digital form internally

Analog systems are different from digital systems because

1. they use transistors
2. they handle information in analog form
3. they handle information in digital form
4. they are slow

Answer – (2) they handle information in analog form

Why are digital circuits easier to design than analog circuits?

1. They do not control electricity precisely over a wide range.
2. They are made in the form of ICs.
3. All elements of digital circuits are from the same family.
4. 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

1. about a second
2. about a hundredth of a second
3. a few billionths of a second
4. a few milliseconds

Answer – (3) a few billionths of a second

Analog methods are not used for handling extremely precise information because

1. precise information always involves numbers which are inherently digital
2. there are limits to how closely an analog signal can reproduce the information
3. analog information never needs to be precise
4. 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?

1. RTL
2. DTL
3. TTL
4. MOS

Answer – (1) RTL

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

1. rise time
2. decay time
3. propagation tie
4. operating speed

Answer – (1) rise time

The main advantages of CMOS as compared to TTL are

1. lower power consumption and better noise margins
2. lower power consumption with low fanout
3. higher speed operation with low power consumption
4. 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

1. totem-pole
2. chip
3. bipolar
4. loading-point

Answer – (1) totem-pole

Which of the following boolean algebra statements represent distributive law

1. (A + B) + C = A + (B + C)
2. A . (B + C) = (A . B) + (A . C)
3. A . (B . C) = (A . B) . C
4. None of these

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

Which of the following boolean algebra statements represent commutative law

1. (A + B) + C = A(B + C)
2. A . (B + C) = (A . B) + (A . C)
3. A + B = B + A
4. A + A = A

Answer – (3) A + B = B + A

Which of the following logic expression is incorrect?

1. 1 ⊕ 0 = 1
2. 1 ⊕ 1 ⊕ 0 = 1
3. 1 ⊕ 1 ⊕ 1 = 1
4. 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

1. X + Y
2. X . Y
3. X . Y
4. X . Y

Answer – (2) X . Y

What logic gate is represented by the circuit shown below

1. NAND
2. NOR
3. AND
4. EQUIVALENCE

Answer – (3) AND

The boolean expression A + BC equals

1. (A + B) (A + C)
2. (A + B) (A + C)
3. (A + B) (A + C)
4. none of these

Answer – (2) (A + B) (A + C)

The clock signals are used in sequential logic circuits to

1. tell the time of the day
2. tell how much time has elapsed since the system was turned on
3. carry serial data signals
4. 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

1. NAND gate
2. NOR gate
3. AND gate
4. OR gate

Answer – (2) NOR gate

The term product-of-sum in Boolean algebra means

1. AND function of several OR functions
2. OR function of several AND functions
3. OR function of several OR functions
4. AND function of several AND functions

Answer – (1) AND functions of several OR functions

An n-stage ripple counter can count up to

1. 2^n
2. 2^n – 1
3. n
4. 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. 1 MHZ
2. 2 MHZ
3. 4 MHZ
4. 8 MHZ

Answer – (1) 1 MHZ

Non-volatility is an important advantage of

1. CCD’s
2. RAM
3. PROM
4. EPROM

Answer – (3) PROM

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