Understand ‘What Is Combinational Circuit’ Before You Regret!

Understand ‘What Is Combinational Circuit’ Before You Regret!

A combinational circuit is one in which the various gates in the circuit, such as the encoder, decoder, multiplexer, and demultiplexer, are combined.

Job-Oriented Offline VLSI Courses banner

What are the Properties of a Combinational Circuit?

  • At any given point, the output of a combinational circuit is determined solely by the levels existing at the input terminals; it does not require memory. The prior state of the input has no bearing on the circuit’s current state.
  • A combinational circuit can have as many as n inputs and m outputs.
  • Combinational Logic Circuits do not use any memory. They are digital logic circuits whose output is wholly determined at any one time by the combination of their inputs.
  • As combinational logic circuits have “no memory,” “timing,” or “feedback loops” built in by default, if one of its inputs changes state from 0-1 to 1-0, the consequent output will change as well.

Also read- Congestion in VLSI Physical Design Flow

What are Combinational Circuits made of?

Combinational Logic Circuits are built up of fundamental logic gates such as NAND, NOR, and NOT. These gates are “combined” or joined together to create more complex switching circuits. Combinational logic circuits are built around these logic gates.

A decoder is an example of a combinational circuit; it translates binary code data at its input into a number of separate output lines. Each output line provides an equivalent decimal code at its output.

What are the Functions of a Combinational Circuit?

The function of a combinational logic circuit can be specified in three ways:

  1.   Boolean Algebra – This is an algebraic equation that shows how the logic circuit works for each True or False input variable that results in a logic “1” output.
  2. Truth Table – A truth table specifies the function of a logic gate by displaying all of the output states in tabular form for each conceivable combination of input variables that the gate may encounter.
  3. Logic Diagram – This is a graphical depiction of a logic circuit that depicts the wiring and connections of each particular logic gate that implements the logic circuit, which is represented by a specific graphical symbol.


Combinational logic circuits can be extremely basic or extremely complex. Any combinational circuit can be created using only NAND and NOR gates, which are considered “universal” gates. Know more about these combinational circuits by enrolling in a course on Chipedge which is the best VLSI training institute in India for online VLSI trainingThere are several online VLSI courses on this website that include a VLSI design course as well. 

Also read- What is Clock Tree Synthesis?

 Image Source

Share This Post:

The Role of Layout Design Rules in VLSI

Read More

What is VLSI Programming And How Does It Impact Chip Design?

Read More

5 Common Fault Models In VLSI

Read More

8 Common Mistakes to Avoid in VLSI Job Applications

Read More

What is SystemVerilog: The Language for Modern Hardware Design and verification

Read More

VLSI Basics: Unveiling the Microworld

Read More

Course Categories

Subscribe to our Blog

Get the latest VLSI news, updates, technical and interview resources

Get Upto 40% OFF