In this article, we are going to learn about the Digital Electronics Interview Questions And Answers in a very detailed manner. This question we have covered is most important for interviews.
You can also Buy the best books to learn more about the digital electronics subject. You can purchase from the below link:
List Of Best Books For Digital Electronics For GATE, ESE PSUs
Also read
- AND Gate Truth Table – Details, Symbol & Circuit Diagram
- What is VRLA Battery?
- Cathode Ray Oscilloscope (CRO)
- OSI Reference Model: Layers, Characteristics, Functions
Digital Electronics Interview Questions
Que.1: Given two X-OR gates, make one as a buffer and one as an inverter.
Answer: If we tie one input of X-OR as 1 then it will act as an Inverter. If we tie one input of X-OR as 0 then it will act as a Buffer.
Que.2: Tell some applications of Buffer.
Answer: They are used to introduce delays in digital circuits. They are used to eliminate cross-talk due to inter-electrode capacitance due to close routing. They are used to support high fan-out.
Que.3: Give two methods of converting a two-input NAND gate to an inverter.
Answer: Method 1: Short both the inputs of the NAND gate and apply the signal then it will act as an Inverter. Method 2: Connect the output to one of the inputs and the other to the input signal.
Que.4: Why are most interrupts active low?
Answer: If you consider the transistor level of a module, active low means the capacitor in the output terminal gets charged or discharged based on low-to-high and high-to-low transition respectively. When it goes from high to low it depends on the pull-down resistor that pulls it down and it is relatively easy for the output capacitance to discharge rather than charge. hence people prefer using active low signals.
Que.5: Difference between Latch and Flip-flop.
Answer: The latch is a level-sensitive device whereas the flip-flop is an edge-sensitive device. flip-flops are made up of latches only.
Que.6: What is a multiplexer?
Answer: It is a combinational circuit that selects binary information from one of many input lines and directs it to a single output line.
Que.7: What is a major advantage of R-2R ladder DAC as compared to binary-weighted DAC?
Answer: The R-2R ladder uses only two values of resistors in the circuits while n binary-weighted DAC various values of resistors are required which depends on the number of binary bits.
Que.8: What is the accuracy of a Digital to Analog Converter?
Answer: It is the comparison between the actual output of the converter and its expected output.
Que.9: No. of unused states in the 3-bit Jhonson’s counter is?
Answer: To find out the unused states in Jhonson’s Counter we can use the formula: 2n-2n. So unused states in the 3-bit Jhonson’s counter = 23-6 =2
Que.10: What is Digital Gate?
Answer: Digital gates are basically electronic components that are used for switching and manipulating binary data
Que.11: What do you mean by the universal gate?
Answer: The universal gates are those from which we can make any gate by using them. The universal gates are: NAND and NOR
Que.12: What is a magnitude comparator?
Answer: A digital comparator or magnitude comparator is a hardware electronic device that takes two numbers as input in binary form and determines whether one number s greater than, less than, or equal to the other number.
Comparators are used in the central processing units (CPU) and microcontrollers.
Que.13: What is Flip-flop?
Answer: Flip-flop is a sequential device that is used to store 1 bit.
Que.14: How many types of flip-flops are used in digital circuits?
Answer: J-K flip-flop, S-R flip-flop, D flip-flop, T flip-flop.
Que.15: What is the disadvantage of SR flip-flop?
Answer: In SR flip-flop, if both the inputs are at logic 1 then it gives invalid output.
Que.16: What is the disadvantage of the JK flip-flop?
Answer: In JK flip-flop there will be a race around the condition that occurs when both the inputs are at logic 1. To remove race-around conditions, we have to use a master-slave flip-flop or we have to use an edge-sensitive flip-flop.
Que.17: What is the race-around condition of the JK flip-flop?
Answer: For the JK flip-flop, if J=K=1, and if clk=1 for a long period of time, then output Q will toggle as long as CLK remains high which makes the output unstable or uncertain. This is called a race-around condition in the JK flip-flop.
Que.18: What is the Shift register?
Answer: The shift register is a device that is used for storing and processing the bit in serial or parallel.
Que.19: What are the types of Shift registers?
Answer: Serial In Serial Out (SISO), Serial In Parallel Out (SIPO), parallel In Serial Out (PISO), Parallel In Parallel Out (PIPO)
Que.20: What is Setup Time?
Answer: A minimum time period during which data must be stable before the clock makes a valid transition. For example: For a positive edge-triggered flip-flop having a setup time of 2 ns then input data should be stable for 2 ns before the clock make a valid transition from zero to one.
Que.21: What is Hold Time?
Answer: A minimum time period during which data must be stable after the clock has made a valid transition. For example: For an edge-triggered flip-flop, with a hold time of 1 ns, then input data should be stable for at least 1 ns after the clock has made the transition.
Que.22 What does Boolean algebra deal with?
Answer: Boolean algebra is the category of algebra in which the variable’s values are the truth values, true and false, ordinarily denoted 1 and 0 respectively. It is used to analyze and simplify digital circuits or digital gates. It is also called Binary Algebra or logical algebra.
Boolean Algebra Operations:
- The basic operations of Boolean algebra are as follows:
- Conjunction or AND operation
- Disjunction or OR operation
- Negation or Not operation
Que.23 What are the different ways of minimizing logical expressions in a digital system?
Answer: To minimize a logical expression 3 different methods are used:
- Boolean algebra: when a number of variables are less and the output is 0 or 1.
- The k-map technique: can be used for up to 5 variables.
- Tabulation method: this method can be used for any number of variables.
Que.24 What are the different Boolean theorems? What is the advantage of using Boolean theorems?
Answer:
- Different Boolean theorems used to minimize the logic expressions are:
- Distribution theorem
- Consensus theorem
- De Morgan’s theorem
- Transposition theorem
- Advantages of using Boolean theorems:
- The number of logic gates was reduced.
- Speed of operation improves.
- Power dissipation decreases.
- Complexity reduces.
Que.25 What is Dual Expression in a digital system? What is a self-dual expression?
Answer:
- Dual expression is used to convert positive logic into negative logic or vice-versa.
- Self-dual expression: when a variable dual is equal to the variable itself, it is called self-dual.
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