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APRESENTATION ON
ANALYSIS OF DIFFERENT LOGIC FULL ADDERS
BYA.GUNA SEKHAR
11HR1A04011
CONTENTS
Need of adders
Basic parameters
Full adder
C-CMOS logic full adder
CPL
DPL
Transmission gate full adder
Transmission function full adder
14T Full adder
GDI XOR/XNOR Full adder
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WHAT IS THE NEED OF ADDERS??
Addition is the basic arithmetic operation
Core of arithmetic operation like multiplication,
subtraction, division etc.,
Adder is the key element for VLSI Systems like
ALU,s
Microprocessors
Parity checkers
Code converters
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BASIC PARAMETERS
As any VLSI System basic requirements:
Similarly for Full adder circuit requires:
Power consumption
Speed
Area
PDP
Delay
Power dissipation
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FULL ADDER
For three bit addition
Accept a carry bit from a previous stage
C = AB + ACin + BCin
S = A'B‘Cin + A'BCin'+AB'Cin'+ABCin
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A B Cin Cout S
0 0 0 0 0
0 0 1 0 1
0 1 0 0 1
0 1 1 1 0
1 0 0 0 1
1 0 1 1 0
1 1 0 1 0
1 1 1 1 1
DIFFERENT LOGICS OF FULL ADDER
C-CMOS logic full adder
Pass transistor logic
CPL
DPL
Transmission gate full adder
Transmission function full adder
14T Full adder
GDI XOR/XNOR Full adder
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C-CMOS LOGIC FULL ADDER
Conventional CMOS
24 transistors
Structure is based on pull up & pull down
High noise margin
Stability at low voltages
Less number of interconnecting wires
Weak output driving capability
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8
Cont. ,
C-PASS TRANSISTOR LOGIC
Complementary Pass Transistor Logic
24 transistors
Each signal is carried by two wires
Faster than CMOS
High power consumption
Wiring complexity
High delay
9
10
Cont. ,
DOUBLE PASS TRANSISTOR LOGIC
28 Transistors
Both nMOS and pMOS logic network
Reduces threshold loss problem
Noise margin
Speed
Low power
Requires less area
11
12
Cont. ,
TRANSMISSION GATE FULL ADDER
20 Transistors
Delay is less
High number of internal nodes increase parasitic
capacitance
Additional buffers required
Weak driving capability
More power consumption
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14
Cont. ,
TRANSMISSION FUNCTION FULL ADDER
16 transistors
Two possible short circuit paths to ground
Same delay as C-CMOS and cpl
High noise margin
15
16
Cont. ,
14T FULL ADDER
14 Transistors
Uses hybrid logic styles( more than one logics)
It uses XOR/XNOR circuit with feedback loop
Less driving capability
Noise immunity
17
18
Cont. ,
GDI XOR/XNOR FULL ADDER
10 transistors
It uses XOR/XNOR gate & multiplexers
Consumes less power
Less internal capacitance
Less area
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COMPARISION BETWEEN DIFFERENT LOGICS
Sl No Cell Name Delay Avg power PDP Transistors
1 C-COMOS 0.195 0.345 0.067 24
2 CPL 0.182 0.367 0.032 32
3 DPL 0.167 0.361 0.06 28
4 TG CMOS 0.135 0.305 0.041 20
5 TFA 0.353 0.044 0.015 16
6 14T 0.548 0.049 0.026 14
7 GDI XOR 0.161 1.384 0.223 10
8 GDI XNOR 0.266 0.055 0.014 10
20
REFERENCES
• Mariano Aguirre-Hernandez and Monico Linares-Aranda, “CMOS Full-Adders for Energy-EfficientArithmetic Applications,” in Proc. IEEE VLSI SYSTEMS, 4, April 2011, vol. 19, pp. 718-721.
• A. M. Shams, T. K. Darwish, and M. Bayoumi, “Performance analysis of low-power1-bit CMOS full adder cells,” IEEE Trans. Very Large Scale Integr. (VLSI) Syst., vol. 10, no. 1, pp. 20–29, Feb. 2002.
• S. Goel, A. Kumar, and M. Bayoumi, “Design of robust, energy-efficient full adders for deep-submicrometer design using hybrid-CMOS logic style,” IEEE Trans. Very Large Scale Integr. (VLSI) Syst., vol. 14, no. 12, pp. 1309–1320, Dec. 2006.
• Amir Ali Khatibzadeh, Kaamran Raahemifar, “A study and comparision of full adder cells based on the standard CMOS logic,” IEEE Trans.CCECE, Niagara Falls, May 2004 0-7803-8253, pp. 2139-2142
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THANK YOU
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