Sequential Circuit

A sequential circuit is a digital circuit that has memory. It means the output of the circuit depends not only on the present input but also on the past input. The sequential circuits can be classified into two categories: Synchronous and Asynchronous circuits.

Synchronous circuits are the circuits that use clocks to synchronize the input and output signals. The input signals are sampled at the rising or falling edge of the clock, and the output signals are updated accordingly. Flip-flops, counters, and shift registers are examples of synchronous circuits.

Asynchronous circuits are the circuits that do not use clocks to synchronize the input and output signals. The output signals are updated whenever the input signals change. Asynchronous circuits are slower and more complex than synchronous circuits.

The Answer

The correct answer to the given question is option 'D', i.e., Multiplexer. A multiplexer is a combinational circuit that selects one input signal out of multiple input signals based on the control signals. A multiplexer does not have any memory or feedback, so it is not a sequential circuit.

Conclusion

In conclusion, a sequential circuit is a digital circuit that has memory, and the output depends on the present and past input signals. Synchronous and asynchronous circuits are two categories of sequential circuits. Flip-flops, counters, and shift registers are examples of synchronous circuits, while multiplexers are not sequential circuits.