Parallel Adder: Definition and it’s uses

Parallel adder is a combinatorial circuit adding every bit position of the operands at the same time. Thus it is requiring a number of bit-adders equal to the number of bits to be added. In our every life we are using this (Parallel A). There are a lot’s of electronics devices that using the parallel adder

Definition of parallel adder:

A single full adder performs the addition of two one-bit numbers and an input carry. But a Parallel Adder is a digital circuit capable of finding the arithmetic sum of two binary numbers that are greater than one bit in length by operating on corresponding pairs of bits in parallel.

Circuit diagram of PA :

Figure:Circuit diagram of Parallel adder.
Figure:Circuit diagram of Parallel adder.


A = A3 A2 A1 A0

B = B3 B2 B1 B0

So, the equation is:

Sum S = A ⊕  B ⊕ C    

Carry C = AB+BC+CA 

Working of parallel Adder

  1. As shown in the figure, firstly the full adder FA1 adds A0 and B0 along with the carry C0 to generate the sum S0 (the first bit of the output sum) and the carry C1 which is connected to the next adder in the chain.
  1. Next, the full adder FA2 uses this carry bit C1 to add with the input bits A1 and B1 to generate the sum S1(the second bit of the output sum) and the carry C2 which is again further connected to the next adder in the chain and so on.
  2. The process continues till the last full adder FAn uses the carry bit Cn to add with its input An and Bn to generate the last bit of the output along with last carry bit Cout.

Uses :

Any electronic device you can think of that has a microcontroller or a CPU in it is using an adder. Generally speaking, most home electronics are probably going to use 8bit microcontrollers or 32/64bit CPUs. So if you had a 4-bit adder it would most likely be used with a second 4bit adder to form an 8bit adder.

Examples include Smart thermostats, appliances such as washing machines or driers that have digital readouts, digital alarm clocks, digital wristwatches, digital bathroom scales, game consoles, network equipment such as routers or wifi access points, etc.

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