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Comparison Between Combinational & Sequential Logic

Combinational Logic Vs Sequential Logic

In Digital Electronics, there are two types of logic circuits i.e. combinational logic & sequential logic circuit. Both of these logic circuits are used in digital devices and perform different types of tasks based on their design logic.

Comparison Between Combinational & Sequential Logic

Before going further into the difference and comparison between these two logics, let’s look into what combinational and sequential logic is.

Combinational logic

In combinational logic, the current output depends on the current input. They are also referred to as time-independent circuits as the output of the circuit will only depend on the input at that time & not the previous inputs.

Combinational Logic Circuit

Combinational logic is made up Boolean logic gates where the output is the combination of the present input.

Sequential logic

In sequential logic, the current output of the system depends on the current input as well as the previous input. So they are a time-dependent circuit.

Sequential Logic Circuit

The sequential logic follows a sequence of logical inputs which leads to a specific output. These sequences are stored in memory units called flip-flops or latches. These memory units store the previous data and feedback it into the logic circuit making a sequential logic circuit.

Sequential logic is made up of combinational logic with the addition of memory units.

Comparison Between Combinational & Sequential Logic

Combinational Logic Sequential Logic
Its output depends only on the current input Its output depends on the current as well as previous input.
Only consists of digital logic gates Designed from logic gates as well as memory units
Its processing speed is fast Its processing speed is slow
Combinational logic designing is simple & easy. Its designing is complex as compared to combinational logic
It is independent of the clock signal. Output updates as soon as the input is changed. It updates the output only when the clock signal is applied.
There is no feedback system involved. There is feedback from output to input.
Example of combinational logic circuits are Encoder, multiplexer & adder etc A counter is a simple example of a sequential circuit as it retains and updates its value according to the previous one.

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