## Full Subtractor-

• Full Subtractor is a combinational logic circuit that is used for the purpose of subtracting two single bit numbers taking into consideration borrow of the lower significant stage.
• Thus, Full Subtractor has the ability to perform the subtraction of three bits unlike half subtractor which can subtract only two bits.
• It contains 3 inputs and 2 outputs (Difference and Borrow). ## Designing a Full Subtractor-

### Step-01:

Identify the input and output variables-

• Input variables = A , B , Bin (either 0 or 1)
• Output variables = D , Bout where D = Difference and Bout = Borrow

### Step-02:

Draw the truth table-

 Inputs Outputs A B Bin Bout (Borrow) D (Difference) 0 0 0 0 0 0 0 1 1 1 0 1 0 1 1 0 1 1 1 0 1 0 0 0 1 1 0 1 0 0 1 1 0 0 0 1 1 1 1 1

Truth Table

### Step-03:

Draw the K-maps using the above truth table and determine the simplified Boolean expressions- ### Step-04:

Draw the logic diagram- Logic Diagram

Here, Full Subtractor has been implemented using 1 XOR gate, 3 AND gates and 1 OR gate.

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