Binary Parallel Adder is the digital function that is used to produce the arithmetic sum of two binary numbers in parallel. The two binary numbers must be greater than one bit in length. It consists of full adders connected in cascade with the output carry from each LSB full adder connected to the input carry of the next higher-order full adder. An n bit parallel adder requires n full adders to perform the operation. A four-bit binary parallel consists of four full adders.
For example: Let us take two 4-bit numbers:
A=1011
B=0001
The augend bits are A4, A3, A2, and A1 and the addend bits are B4, B3, B2, and B1. The input carry to the first full adder is C1 and output carry from MSB position full adder is C5 that goes to next higher-order position and all carries are connected in the chain through full adders.
Advantages of parallel Adder/Subtractor
The parallel adder/subtractor performs the addition operation faster as compared to the serial adder/subtractor.
The time required for addition does not depend on the number of bits.
The output is in parallel form i.e all the bits are added/subtracted at the same time.
It is less costly.
Disadvantages of Parallel Adder/Subtractor
Each adder has to wait for the carry which is to be generated from the previous adder in a chain.
The propagation delay( delay associated with the traveling of carry-bit) is found to increase with the increase in the number of bits to be added.
