SUBTRACTORS
Half Subtractor
Half subtractor is a combination circuit with two inputs and two outputs (difference and borrow). It produces the difference between the two binary bits at the input and also produces an output (Borrow) to indicate if a 1 has been borrowed. In the subtraction (A-B), A is called as Minuend bit and B is called as Subtrahend bit.
Full Subtractor
The disadvantage of a half subtractor is overcome by full subtractor. The full subtractor is a combinational circuit with three inputs A,B,C and two output D and C'. A is the 'minuend', B is 'subtrahend', C is the 'borrow' produced by the previous stage, D is the difference output and C' is the borrow output.
Subtraction using 1’s compliment using adder IC
- Take 1’s compliment of 2nd binary number.
- Add to 1st binary number.
- If carry is generated the difference is positive, add carry to LSB.
- If no carry is generated the difference is negative ,take 1’s compliment of result.