Power-Efficient Full Adder using

Cadence Virtuoso
[1]
Nirali Hemant Patel, [2] Jay. R. Patel,
[1]
Student, [2] Student
[1]
niralihoney99@gmail.com, [2] pjayu73@gmail.com

Abstract— Generally, full adder circuit is beneficial for building blocks in many applications, it's utilized in designing ALU
and this ALU is employed for big variety of applications (from designing CPU to GPU). A full adder is often used as a part
of the many other larger circuits like Ripple carry adder, it adds n-bits at a time. ALU- Arithmetic Logic Unit (one of the
circuit may be a full adder). To come up with memory addresses inside a computer and to create the Program Counter point
to next instruction, the ALU makes use of this adder. For graphics related applications, where complex computation is very
much needed, the GPU uses optimized ALU which is formed from full adders and other circuits too. It is implemented using
180nm CMOS technology. Generally, the CADENCE VIRTUOSO tools are used for designing the schematics and to try to
do simulations. The simulation results include 1.8V analog input range at a pulse of 0 to 1.6 V.
Index Terms— ALU, CADENCE VIRTUOSO, Full adder, GPU.

I. INTRODUCTION supply voltage. i.e. vdd to ground [5]. In arithmetic unit

binary addition plays the major role because every
arithmetic operation is performed by using an addition
Now-a-days all the systems are built on an upcoming operation. So building low power and high performance
technology called System on Chip (SoC) in which all adders would affect the system performance and also
the components and peripherals have been built on a reduce the whole power consumption [8]. Design of full
single chip which increases the complexity of the
system. VLSI plays an important role in the adder can be done using different techniques like C-
development of such ideas [7]. In today’s era due to CMOS, CPL, Transmission function and Transmission
technological advancement, there are various gate, GDI, and etc. Analysis of full adder designs:
applications of Full Adder which include the range In binary adder circuit A, B, C act as input bits, SUM
from constructing ripple carry counter to a massive and CARRY act as outputs.
processor chip which includes Snapdragon, Intel
Pentium for CPU parts. Addition is a key fundamental SUM= A ^ B ^ C
function for many error tolerant applications, (1)
approximate addition is considered to be an efficient CARRY= (A^B) *C + AB
technique for trading off energy against performance (2)
and accuracy [1]. The rapid upsurge in the research area
of low power, high speed embedded systems such as The remaining portion of the paper is organized as:
smartphones, laptops, tablets and biomedical devices, Next part of the paper explains architecture of Full
etc., has led the digital circuit designers to scale down Adder then, different types of methods for the structure
the circuit dimensions, so that the storage and logical of full adder with the schematic and their output
density can be increased in a chip. The aim of the waveforms. Afterwards the simulation results are being
designer is to reduce the total power dissipation [4]. In compared with different papers and the proposed paper
past, power dissipation has been the secondary option and shows which is more power-efficient and lastly, the
which is taken in consideration but nowadays, the paper ends with a conclusion followed by the
customers are demanding for portable battery operated references.
devices like mobile phones, smartphones, laptops, etc.
is rapidly increasing. So, the life of battery is the II. ARCHITECTURE OF FULL ADDER
primary concern. Therefore, low power design
technology is required to make them commercially The digital pulse signal is initial applied to the inputs as
viable. In static CMOS circuits, about the 10% of the therefore we all know that Half-adder circuit
aggregate power utilization is because of short out incorporates a major disadvantage that we tend to don't
current. In unique circuits there is no such issue, in light have the scope to provide ‘Carry in’ bit for addition.
of the fact that there is no any prompt dc path from just in case full adder construction, we are able to

1
actually create a carry in input within the circuitry and using multiplexer and a NOT gate, further using Half
will add it with alternative two inputs A and B. So, adder, 10T technique and many more techniques or
within the case of Full Adder Circuit we've got three methods are there. Here, Full adder using Gates, MUX
inputs A, B and Carry in and that we can get final and Half Adder is being implemented in Cadence
output sum and carry out. Virtuoso where Simulation results are also presented
So, A + B + CARRY IN = sum and carry out. over here.

1) Using XOR, AND and OR gates

With the help of TABLE I. and technique of Boolean

algebra,

SUM= A’ B’ C-IN + A’ B C’ + A B’ C’ + A B C
= C (A’ B’ + A B) + C’ (A’ B + A B’)
= C XOR (A XOR B)
Fig. 1. Block Diagram of Full-Adder
CARRY= A B + A C + B C (A + A’)
TABLE I. TRUTH TABLE OF FULL ADDER = A B C + A B + A C+ A’ B C
= A B (1 +C) + A C + A’ B C
= A B + A C + A’ B C
Carry = A B + A C (B + B’) + A’ B C
Carry In Input A Input B SUM
Out
= A B C + A B + A B’ C + A’ B C
= A B (C + 1) + A B’ C + A’ B C
= A B + A B’ C + A’ B C
0 0 0 0 0 = AB + C (A’ B + A B’)
Therefore, COUT = AB + C (A EX – OR B)

0 1 0 1 0

0 0 1 1 0

0 1 1 0 1

Fig. 2. Block Diagram of Full Adder using Gates

1 0 0 1 0

1 1 0 0 1

1 0 1 0 1

1 1 1 1 1

Fig. 3. Test circuit of Full Adder using Gates

III. METHODS FOR FULL ADDER

There are various methods for implementing Full Adder

which includes using only gate like AND, OR and
NOT, moreover, full adder can also be implemented

2
 Fig. 4. Output of Full Adder using Gates

2) Using Multiplexer Fig. 6. Test Circuit of Full Adder using MUX

After the truth table design tables for sum and carry
outputs as shown below:

Fig. 7. Output waveform of Full Adder using MUX

So, two 4x1 multiplexer and a NOT gate is used for 3) Using Half Adder
preparing Full Adder using 4:1 MUX.
2 Half Adders and a OR gate is required to implement a
A Multiplexer is a device which is employed to
Full Adder. Here A, B, C are inputs & SUM and
selectively present output, based off the choice input
CARRY are output.
provided. By cleverly manipulating the Input lines
and therefore the selection lines, we are able to
simulate the logic behind many circuits using

Fig. 8. Block Diagram of Full Adder using Half-Adder

With this logic circuit, two bits can be added together,
taking a carry from the next lower order of magnitude,
and sending a carry to the next higher order of
magnitude

MUX’s. For a Full Adder we've got 2 outputs, sum and

Carry.

Fig 5. Block Diagram of Full Adder using 4:1 MUX

3
 Fig. 9. Test Circuit of Full Adder using Half Adder number of transistor delay and power dissipation.
they're selected for this work since they need been
commonly utilized in many applications. In addition, it
is an important operation for any high speed digital
system, digital signal processing or system. Therefore,
pertinent choice of adder topologies is essentially
important within the design of VLSI integrated circuits
for top speed and high performance CMOS circuits.
With this application of biomedical aspect, power
dissipation, gate count and delay for some adder
topologies discussed earlier are observed.

TABLE II. DIFFERENT METHODS OF FULL

Fig. 10. Output Waveform of Full Adder using Half ADDER
Adder
Parameters Using Using Using
IV. PARAMETERS gates MUX H.A.
Technology 180nm 180nm 180nm
1) Power dissipation
Vdd(V) 1.8 1.8 1.8
The process in which an electric or electronic device Voltage 0 to 1.8 0 to 1.8 0 to 1.8
produces heat or other waste energy as an unwanted Pulses(V)
byproduct of its primary action. Power 232.38p 491.76µ 109.3µ
Measured by doing DC analysis and then multiplying dissipation(W)
the output Voltage and Current we will get the amount Delay(s) 694.4n 749.4n 2.34 µ
of power which is dissipated.
Number of 53 18 18
transistor
2) Delay

The propagation delay of a signal path is the time taken VI. IMPLEMENTED DESIGN
between the change in input and the change in output
for that signal. If it is not managed properly, In the proposed FA design, a low power consumption
propagation delays can result in logic circuits that run Full Adder structure is proposed. Here, the design is
too slowly to meet their requirements, or that fail working at 1.8V input voltage and the pulses are given
altogether. from 0V to 1.8V with the period of (1/1k), (1/2k) and
Measured by doing Transient analysis. (1/4k) for A, B, C respectively for covering every
possibility of output. Furthermore, it is connected to a
V. COMPARISON OF DIFFERENT METHODS low-pass filter. Basically, the design of Full Adder is
formed with different methods. So, here Full Adder
Adders are one among the foremost widely digital using gates (Method-1) is used as it gives efficient
components within the digital microcircuit design and results according to the criteria of having low power
are the required a part of Digital Signal Processing dissipation.
(DSP) applications. With the advances in technology,
researchers have tried and try to style adders which VII. RESULT AND DISCUSSION
supply either high speed, low power consumption, less
area or the mixture of them. during this paper, the Here, Full adder is being prepared with an input voltage
planning of varied adders like Ripple Carry Adder, of 1.8V, moreover full adder is used in almost every
Carry Skip Adder, Carry Increment Adder, Carry Look circuit where ALU is taken into consideration so the
Ahead Adder, Carry Save Adder, Carry Select Adder, aspect of Biomedical application is taken into
Carry Bypass Adder are discussed and are compared on consideration for this research. The power dissipation is
the idea of their performance parameters like area, quite low compared to [2], [3] & [4] that is 232.38pW
delay and power distribution. The performances of due to the usage of simple technique of gates and the
adder topologies are discussed for robustness against efficient way for it. But at the cost of speed, because for

4
maintaining other aspects delay increases over here Engineering and Technology, Vol. 8, Issue 5, May
with 694.4ns. Furthermore, number of transistor which 2019.
are used over here are 53. As the main aspect of this
research is low power consumption and it is fulfilling [2] Radhika P, Aswathi Gopan, “Low Power and Area
that aspect. Efficient Full Adder using GDI and 2T XNOR”,
International Journal of Innovative Technology and
TABLE III. COMPARISON OF RESULTS Exploring Engineering (IJITEE) ISSN: 2278-3075,
Volume-8, Issue- 6S4, April 2019.
[3] S.Vasantha swaminathan, J.Surendiran, B.P.Pradeep
Parameters This [2] [3] [4] kumar, “Design and Implementation of Kogge Stone
work adder using CMOS and GDI Design: VLSI Based”,
International Journal of Engineering and Advanced
Technology 180n 180n 180n 180n Technology (IJEAT) ISSN: 2249 – 8958, Volume-8
m m m m Issue-6S3, September 2019.
Vdd(V) 1.8 1.8 1.8 1.8
[4] Khoirom Johnson Singh, Tripurari Sharan, Huirem
Voltage 0 to 0 to 0 to 0 to Tarunkumar ,“High Speed and Low Power Basic
Pulses(V) 1.8 1.8 1.8 1.8 Digital Logic Gates, Half-Adder and Full-Adder Using
Power 232.3 0.340 13.49 189. Modified Gate Diffusion Input Technology”, Journal of
dissipation( 8p 1µ 3µ 4µ VLSI Design Tools & Technology ISSN: 2249-474X
W) (Online), ISSN: 2321-6492 (Print) Volume 8, Issue
Delay(s) 694.4 0.223 41.43 0.48 1..2018.
n 1p n n
No. of 53 10 40 30 [5] Sandeep Dhariwal, Harinath Aireddy, Prajwal
transistor Kumar K V, Ravi Shankar Mishra, “Low Power
Dissipation in Adder using Isolated Sleepy Keeper
CONCLUSION Approach”, Alliance International Conference on
Artificial Intelligence and Machine Learning
The proposed work presents a highly digital Full adder (AICAAM), April 2019.
whose major parts are synthesizable, reducing the [6] Akshitha, Niju Rajan , “ Power Reduction of Half
design efforts, time-to-market and power requirement, Adder and Half Subtractor Using Different Partial
it's scalable with the technology. Having an application Adiabatic Logic Styles”, International Conference on
of Biomedical by keeping now-a-days severity in mind Intelligent Sustainable Systems (ICISS 2019) IEEE
of the welfare of the people. This particular Full adder Xplore Part Number: CFP19M19-ART; ISBN: 978-1-
is employed for this type of application where number 5386-7799-5,2019.
of people are counted. The power dissipation of full
adder using gates is 232.38pW, using MUX is [7] S. Selvi*, S. Pradeep, “6 Transistor Full Adder
491.76µW, using Half Adder is 109.3µW. Moreover, Circuit Using Pass Transistor Logic”, Journal of
number of transistors for full adder using gates, MUX Chemical and Pharmaceutical Sciences , ISSN: 0974-
and H.A. are 53, 18 and 18 respectively. The circuits 2115, Special Issue 1: February 2017.
are simulated in CADENCE virtuoso tool using 180 nm
CMOS technologies. The varied analysis like DC and [8] Kalicherla Himabindu, Mr. K.Hariharan,“DESIGN
transient analysis are performed for above said OF AREA AND POWER EFFICIENT FULL ADDER
functional blocks with the assistance of CADENCE IN 180nm”, International Conference on Networks &
tool. Furthermore, another solution is to use different Advances in Computational Technologies (NetACT),
techniques for the low power consumption like using 2017.
Pass Transistor Logic, Hybrid technique and CPL
technique.

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