Combinational Vs. Sequential Circuit: Know the Difference Between Combinational and Sequential Circuit
Both the sequential and combinational circuits are the most widely used ones in the arena of digital electronics. They constitute two broad categories of circuits. Now let’s talk about the difference between combinational and sequential circuits.
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Out of these two circuits- one is very much time-dependent, and the other one is independent. The combinational circuit is time-independent. The output it generates does not depend on any of its previous inputs. On the other hand, sequential circuits are the ones that depend on clock cycles. They depend entirely on the past as well as the present inputs for generating output.
What is a Combinational Circuit?
- The output of a Combinational Circuit depends entirely on the present input.
- It exhibits a faster speed.
- It is comparatively easier to design.
- No feedback is present between the input and output.
- The combinational circuit depends on time.
- Logic gates form the building blocks of such circuits.
- One can make use of it for both boolean and arithmetic operations.
- They don’t hold the capacity of storing any state.
- These circuits do not have a clock- thus, they don’t require triggering.
- They do not possess any memory element.
- Users can feasibly use as well as handle them.
- Example – Demultiplexer, Multiplexer, Decoder, Encoder, etc.
What is a Sequential Circuit?
- The output of a Sequential Circuit depends on both- past as well as present inputs.
- It works at a comparatively slower speed.
- The design of these circuits is comparatively much tougher than the Combinational Circuit.
- A feedback path exists between the output and the input.
- The circuit is time-dependent.
- Flip-flops constitute the building blocks of such a circuit.
- People mainly use them for storing data and information.
- They possess the capability of storing any data state or retaining an earlier state at any given point.
- Because a Sequential circuit depends on a clock, it usually requires triggering.
- They always possess a memory element.
- A user may not be able to handle and use these circuits easily.
- For Example – Counters, Flip-flops, etc.
Difference Between Combinational and Sequential Circuit
| Parameters | Combinational Circuit | Sequential Circuit |
| Meaning and Definition | It is a type of circuit that generates an output by relying on the input it receives at that instant, and it stays independent of time. | It is a type of circuit in which the output does not only rely on the current input. It also relies on the previous ones. |
| Feedback | A Combinational Circuit requires no feedback for generating the next output. It is because its output has no dependency on the time instance. | The output of a Sequential Circuit, on the other hand, relies on both- the previous feedback and the current input. So, the output generated from the previous inputs gets transferred in the form of feedback. The circuit uses it (along with inputs) for generating the next output. |
| Performance | We require the input of only the current state for a Combinational Circuit. Thus, it performs much faster and better in comparison with the Sequential Circuit. | In the case of a Sequential Circuit, the performance is very slow and also comparatively lower. Its dependency on the previous inputs makes the process much more complex. |
| Complexity | It is very less complex in comparison. It is because it basically lacks implementation of feedback. | This type of circuit is always more complex in its nature and functionality. It is because it implements the feedback, depends on previous inputs and also on clocks. |
| Elementary Blocks | Logic gates form the building/ elementary blocks of a Combinational Circuit. | Flip-flops form the building/ elementary blocks of a Sequential Circuit. |
| Operation | One can use these types of circuits for both- Boolean as well as Arithmetic operations. | You can mainly make use of these types of circuits for storing data. |
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