Combinational Circuits Questions and Answers for Viva

Answer-1: A combinational circuit is a digital circuit where the output at any instant depends only on the present combination of inputs.

Answer-2: Basic building blocks include logic gates such as AND, OR, NOT, XOR, NAND, and NOR gates.

Answer-3: Combinational circuits produce outputs solely based on current inputs, while sequential circuits store information and generate outputs based on both current inputs and the circuit's state.

Answer-4: A truth table is a table that lists all possible input combinations for a combinational circuit along with their corresponding outputs.

Answer-5: Boolean algebra is a mathematical system used to analyze and simplify digital circuits. It deals with variables that can take on only two values: true (1) and false (0).

Answer-6: A decoder is used to convert a binary code into a one-hot or decoded output.

Answer-7: A multiplexer selects one of several input lines and forwards it to a single output line, based on a control signal.

Answer-8: A demultiplexer takes a single input line and directs it to one of several possible output lines, depending on the value of its control inputs.

Answer-9: An encoder converts a set of inputs into a smaller set of outputs, usually in binary form.

Answer-10: A priority encoder is an encoder that assigns priority to its input lines. It outputs the binary representation of the highest-priority active input.

Answer-11: A full adder adds three binary inputs (A, B, and a carry-in) to produce a sum and a carry-out.

Answer-12: A half adder adds two binary inputs (A and B) to produce a sum and a carry-out.

Answer-13: A subtractor circuit subtracts one binary number from another. It typically consists of XOR and AND gates.

Answer-14: A comparator is a combinational circuit that compares two binary numbers to determine whether one is greater than, less than, or equal to the other.

Answer-15: A magnitude comparator compares the magnitudes of two binary numbers without considering their sign.

Answer-16: A multiplexer-based adder uses multiplexers to select the carry-in for each bit addition, allowing for parallel computation of the sum and carry-out.

Answer-17: A half adder can only add two bits and does not account for a carry-in, while a full adder can add three bits, including a carry-in.

Answer-18: A barrel shifter is a combinational circuit that shifts a binary number by a specified number of bits in either the left or right direction.

Answer-19: A carry-lookahead adder is a high-speed adder that reduces the propagation delay associated with carry propagation in conventional adders by generating carry signals in advance.

Answer-20: A BCD (Binary Coded Decimal) adder adds two BCD numbers and produces a BCD sum, ensuring that the result is in valid BCD format.