Combinational Circuit vs Sequential Circuit

Overview of combinational and sequential circuit

In digital electronics the circuits are classified into two categories they are combinational and sequential circuits. The Combinational circuits can be termed as the time-independent circuits which do not depend on the previous inputs to generate any desired output.

On the contrary, the  Sequential circuits are the clock cycles dependent. The sequential circuits depend on the present as well as past inputs to generate the output.

What is Combinational Circuit?

In Combinational Circuit the output depends only on the present input.The speed of this circuit is fast. And It can be designed by anyone so easily.

Elementary building blocks are the Logic gates which are Used for the arithmetic as well as for the boolean operations.

In case of the Combinational circuits, they don’t have the capability to store any state of their own hence there is no feedback between input and output. in the combinational circuit, the time is independent.

The combinational circuit does not have a clock so there won’t be any triggering. These circuits will not have any memory element.

They are  easy to use and handle.The design part of the combinational circuits are really easy to implement.

Examples – Encoder, Decoder, Multiplexer, Demultiplexer

What is Sequential Circuit?

The Sequential Circuits  are those whose output depends upon present as well as past input.

They are designed tough as compared to combinational circuits.

In the Sequential circuits, there exists a feedback path between input and output. its is also time-dependent and slow compared to the combinational circuit

The Elementary building blocks of the sequential circuits are Flip-flops.they are mainly used for storing the  data.

Since the sequential circuits are clock-dependent they need to do the triggering. The sequential circuits have memory elements That are not easy to use and handle.

Examples – Flip-flops, Counters

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Table of Difference

Basis of comparisonCombinational circuitsSequential circuits
Storage capacityNot storing any dataStores data
ClockNo clock is usedClock is used
ApplicationUsed in adders, encoders and multiplexersUsed in flip flops
BasicOutput does not depends upon the present inputOutput depends upon the present output
FeedbackNo feedback is requiredFeedback is required

Pivotal Differences Between Combinational and Sequential Circuit

  • The combinational circuit doesn’t have the potential to store the data, on the other hand the  sequential circuits can store a specific amount of data.
  •  The combinational circuits use the current input for generating the output; on the contrary the sequential circuits input decides the  current output of the given input by considering their  previous output.
  • No clock used in the combinational circuit. Where as in the , sequential circuits clock is used.
  • Sequential circuits are used in flip-flops, latches and registers. On The other hand in combinational circuits the basic devices like adders, subtracters, encoders so on.
  • The sequential circuit needs the feedback for their  functioning, on the other hand the combinational circuit does not require any feedback.


The sequential circuit needs the previous outputs for its functioning in order to produce accurate results whereas the devices built using the combinational circuit do not require the previous output for its operation.

Comparison Video