Important Digital Electronics Interview Questions
Q.Define combinational logic
When logic gates are connected together to produce a specified output for certain
specified combinations of input variables, with no storage involved, the resulting circuit is called combinational logic.
Q. Define Half adder and full adder
The logic circuit that performs the addition of two bits is a half adder. The circuit that
performs the addition of three bits is a full adder.
Q. Define Decoder
A decoder is a multiple – input multiple output logic circuit that converts coded inputs into coded outputs where the input and output codes are different.
Q. What is binary decoder?
A decoder is a combinational circuit that converts binary information from n input lines to a maximum of 2n out puts lines.
Q. Define Encoder?
An encoder has 2n input lines and n output lines. In encoder the output lines generate the binary code corresponding to the input value.
Q. What is priority Encoder?
A priority encoder is an encoder circuit that includes the priority function. In priority encoder, if 2 or more inputs are equal to 1 at the same time, the input having the highest priority will take precedence.
Q. Define multiplexer
Multiplexer is a digital switch. If allows digital information from several sources to be routed onto a single output line.
Q. What do you mean by comparator
A comparator is a special combinational circuit designed primarily to compare the relative magnitude of two binary numbers.
Q. What are the classification of sequential circuits?
The sequential circuits are classified on the basis of timing of their signals into two types. They are,
1)Synchronous sequential circuit.
2)Asynchronous sequential circuit.
Q. Define Flip flop.
The basic unit for storage is flip flop. A flip-flop maintains its output state either at 1 or 0 until directed by an input signal to change its state.
Q.What are the different types of flip-flop?
There are various types of flip flops. Some of them are mentioned below they are,
RS flip-flop
SR flip-flop
D flip-flop
JK flip-flop
T flip-flop
Q.What is the operation of D flip-flop?
In D flip-flop during the occurrence of clock pulse if D=1, the output Q is set and if D=0, the output is reset.
Q. What is the operation of JK flip-flop?
• When K input is low and J input is high the Q output of flip-flop is
set.
• When K input is high and J input is low the Q output of flip-flop is
reset.
• When both the inputs K and J are low the output does not change
• When both the inputs K and J are high it is possible to set or reset the flip-flop (ie) the output toggle on the next positive clock edge.
Q. What is the operation of T flip-flop?
T flip-flop is also known as Toggle flip-flop.
• When T=0 there is no change in the output.
• When T=1 the output switch to the complement state (ie) the output
toggles.
Q. Define race around condition.
In JK flip-flop output is fed back to the input. Therefore change in the output results change in the input. Due to this in the positive half of the clock pulse if both J and K are high then output toggles continuously. This condition iscalled ‘race around condition’.
Q. What is edge-triggered flip-flop?
The problem of race around condition can solved by edge triggering flip flop. The term edge triggering means that the flip-flop changes state either at the positive edge or negative edge of the clock pulse and it is sensitive to its inputs only at this transition of the clock.
Q. What is a master-slave flip-flop?
A master-slave flip-flop consists of two flip-flops where one circuit serves as a master and the other as a slave.
Q.Define registers.
A register is a group of flip-flops flip-flop can store one bit information. So an n-bit register has a group of n flip-flops and is capable of storing any binary information/number containing n-bits.
Q.Define shift registers.
The binary information in a register can be moved from stage to stage within the register or into or out of the register upon application of clock pulses. This type of bit movement or shifting is essential for certain arithmetic and logic operations used in microprocessors. This gives rise to group of registers called shift registers.
Q.What are the different types of shift type?
There are five types. They are,
Serial In Serial Out Shift Register
Serial In Parallel Out Shift Register
Parallel In Serial Out Shift Register
Parallel In Parallel Out Shift Register
Bidirectional Shift Register
Q.Define synchronous sequential circuit
In synchronous sequential circuits, signals can affect the memory elements only at discrete instant of time.
Q. Define Asynchronous sequential circuit?
In asynchronous sequential circuits change in input signals can affect memory element at any instant of time.