4 Bit Parallel Adder Block Diagram. 4 bit parallel adder. Addend and augend bits are applied concurrently at inputs to the full adders.
A parallel adder adds corresponding bits simultaneously using full adders. In the block diagram a 0 and b 0 represent the lsb of the four bit words a and b. Carry produced in the lower significant stage is transferred to the subsequent higher stage therefore this can be added there.
A full adder adds two 1 bits and a carry to give an output.
Fig 7 shows block diagram of carry increment adder where the inputs a and b of 8 bits are added using 4 bit ripple carry adders. A simplified schematics of the circuit is shown below. Addend and augend bits are applied concurrently at inputs to the full adders. Carry produced in the lower significant stage is transferred to the subsequent higher stage therefore this can be added there.
