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Introduction
The main difference between sequential and combinational logic circuits is that the sequential circuit consists of just logic gates. In contrast, sequential logic circuits are composed of memory elements and logic gates.
A key aspect that differentiates the sequential and combinational logic circuits is the status of the output elements.
The element output of the circuit is based solely on the current condition of the elements in the input. The output of the sequential circuit depends on the input’s current condition and the output’s past state.
We will also discuss the other important differences between sequential and combinational logic circuits with the aid of this article.
What is a Combinational Circuit?
A combinational circuit could be defined as a circuit whose output depends only on inputs at the same moment.
The example of Combinational Circuit include:
- Half Adder
- Full Adder
- Half Subtractor
- Full Subtractor
What is a Sequential Circuit?
A sequential circuit is defined as a circuit whose output is not just based on the current inputs but also on the previous time of inputs.
Examples of a Sequential circuit are:
- Flip-Flops
- Registers
- Counters
The Key Differences Between Combinational and Sequential Logic Circuit
- Sequential and combinational logic circuits are the basic building blocks of digital circuits. However, the existence of memory elements makes the main difference. The circuit for combination doesn’t have a memory element, while a sequential circuit is composed of memory elements.
- Sequential and combinational logic circuits can generate different outputs. The output from the circuit for combination is a function of the current inputs. However, the output generated by the sequential circuit is dependent on the prior output and current input.
- The feedback loop isn’t included in combinational logic circuits. However, any sequential logic circuit should contain it to monitor the output of previous cycles.
- The clock signal isn’t utilized in the combinational circuit. However, sequential utilize clock signals to ensure synchronization.
- The design process for the combinational circuit is simpler than that in the conventional circuit.
In-Depth Differences Between Combinational and Sequential Circuits
| Point of Difference | Combinational Circuits | Sequential Circuits |
| Definition | A combinational circuit is a digital circuit type where the output is only a pure function of the present input. | The sequential circuit is a digital circuit type whose output relies not just on the current values of the input signals it has but it depends on the past sequence of inputs as well. |
| Memory Unit | Another distinction between sequential circuits and combinational circuits is that a memory device is absent in combinational circuits. | An integrated storage unit for sequential circuits can store instant results. |
| Output | A circuit’s output from a combined circuit relies on the input at present. | On the other hand, the output of the sequential circuit will depend on the recent outputs and current input. |
| Clock | There’s no combinational clock present in a circuit. | However, the possibility of a clock is there in the sequential circuit. |
| Examples | Demultiplexer, decoder, full adder encoder, and half adder are a few examples of combinatorial circuits. | Registers and Flip Flops are a few examples of sequential circuits. |
The sequential circuit contains memory elements. A storing element is included to keep the different data about the stable state levels. This assists in linking the feedback data of the past to current information.
A half adder can be described as a combinatorial logic circuit with two outputs and inputs. Half adder circuits add two binary single-bit numbers, A and B. It is the most basic construction block to add two single-bit numbers. We can define a combinational logic circuit as an electronic circuit whose outputs depend on the condition that its inputs are in. Mathematically speaking, outputs solely depend on the inputs.
The major distinction between these circuits is the outputs of circuits and rely on the current input.
In contrast, the output of sequential circuits relies on the current input and also on the previous outputs. In essence, sequential circuits are much more complicated than combinational ones.
