Question

Which of the following circuits is a sequential circuit?

• A. Multiplexer
• B. Decoder
• C. Flip-Flop
• D. Adder

Hint:

A simple way to distinguish them: If a circuit uses a clock signal to synchronize state changes or has a feedback loop to store data, it is almost certainly a sequential circuit.

Answer 1

The Correct Option is C

Concept: Digital logic circuits are broadly classified into two categories based on their dependence on timing and memory:
• Combinational Circuits: The output at any time depends only on the present combination of inputs. They do not have memory elements. Examples: Adders, Multiplexers, Decoders, Encoders.
• Sequential Circuits: The output depends not only on the present inputs but also on the past history of inputs (previous states). They contain memory elements. Examples: Flip-Flops, Counters, Registers.

Step 1: Analyzing the nature of Combinational Options.
Multiplexers (A), Decoders (B), and Adders (D) are all combinational logic circuits. In an Adder, for instance, the sum is generated immediately based on the current bits being added. There is no internal "state" maintained once the inputs are removed.

Step 2: Identifying the Sequential component.
A Flip-Flop is the most basic storage element in digital electronics. It is capable of storing one bit of information (0 or 1). Because it "remembers" its previous state and uses feedback to maintain that state, it is categorized as a sequential circuit.

Step 3: Conclusion.
Since a sequential circuit must have a memory component, and among the given options only the Flip-Flop possesses memory, option (C) is the correct answer.