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Arithmetic Circuits

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Arithmetic circuits can perform seven different arithmetic operations using a single composite circuit. 
It uses a full adder (FA) to perform these operations. A multiplexer (MUX) is used to provide different inputs to the circuit in order to obtain different arithmetic operations as outputs.

4-bit Arithmetic Circuit : 
Consider the following 4-bit Arithmetic circuit with inputs A and B. It can perform seven different arithmetic operations by varying the inputs of the multiplexer and the carry (C0).

Truth Table for the above Arithmetic Circuit :

S0 S1 C0 MUX Output Full Adder Output

0

0

0

B

A + B

0

0

1

B

A + B + 1

0

1

0

B’

A + B’

0

1

1

B’

A + B’ + 1 = A – B

1

0

0

0

A

1

0

1

0

A + 1

1

1

0

1

A – 1

1

1

1

1

A – 1 + 1 = A

Hence, the different operations for the inputs A and B are –

  1. A + B (adder)
  2. A + B + 1
  3. A + B’
  4. A – B (subtracter)
  5. A
  6. A + 1 (incrementer)
  7. A – 1 (decrementer)

Last Updated : 15 Feb, 2021
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