Combinational Circuits in Digital Logic : Practice MCQ Questions & Answers with Explanations

Explanation: Demultiplexer (Demux) Definition: A demultiplexer (Demux) is a combinational logic circuit that takes a single input signal and channels it into one of several output lines. The specific output line that is selected for the input signal is determined by a set of select lines. It essentially performs the reverse operation of a multiplexer (Mux).

Key Points Frequency-division multiplexing: In telecommunications, frequency-division multiplexing (FDM) is a technique by which the total bandwidth available in a communication medium is divided into a series of non-overlapping frequency bands, each of which is used to carry a separate signal. For example, the coaxial cable used by cable television systems has a bandwidth of about 1000 MHz, but the passband of each television channel is only 6 MHz wide, so there is room for many channels on the cable. Time-division multiplexing: Time-division multiplexing (TDM) is a method of transmitting and receiving independent signals over a common signal path by means of synchronized switches at each end of the transmission line so that each signal appears on the line only a fraction of time in an alternating pattern.

Key Points The combinational circuit is a circuit in which we combine the different gates in the circuit, for example, encoder, decoder, multiplexer and demultiplexer. Some of the characteristics of combinational circuits are following − The output of a combinational circuit at any instant of time depends only on thelevels present at input terminals. The combinational circuit does not use any memory.

Key Points The number of multiplexers required to construct the bus is equal ton, where n is thenumber of bits in each register. The size of each multiplexer must bek: 1 since it multiplexes k data lines, where k is the number of registers. Therefore If there are 8 registers of 16 bits each, then we need 16 multiplexers, each of which is an 8: 1 multiplexer to create the 16-bit data bus.