Half adder layout design

[HALF ADDER DESIGN] April 8, 2013
DECEMBER 2012 SESSION Page 1
ELECTRICAL ENGINEERING DEPARTMENT
EE603-CMOS INTEGRATED CIRCUIT DESIGN
LAB REPORT 6
DESIGNING HALF ADDER CIRCUIT
No Registration No. Name
1. 18DTK10F1036 CHONG WEI TING
2. 18DTK10F1034 ADLAN BIN ABDULLAH
CLASS : DTK 6B
LECTURER : EN. MUHAMAD REDUAN BIN ABU BAKAR
DATE SUBMITTED : 8thARPIL 2013
(Date submitted is one week after date lab)
TUANKU SYED
SIRAJUDDIN
POLYTECHNIC
MARKS
Lab Work :
Lab Report:
Total :

LAB 6 : DESIGNING HALF ADDER CIRCUIT
Aim: Designing half adder circuit using L-edit software.
Objective:
After students had done this laboratory, then students should be able to:
1) Introduce schematic circuit, logic symbols and truth table of half adder.
2) Design half adder circuit using L-edit..
Apparatus: PC-set & L-edit student V 7.12 software.
Half adder is a combinational arithmetic circuit that adds two numbers and produces a
sum bit (S) and carry bit (C) as the output. If A and B are the input bits, then sum bit (S)
is the X-OR of A and B and the carry bit (C) will be the AND of A and B. From this it is
clear that a half adder circuit can be easily constructed using one X-OR gate and one
AND gate. Half adder is the simplest of all adder circuit, but it has a major
disadvantage. The half adder can add only two input bits (A and B) and has nothing to
do with the carry if there is any in the input. So if the input to a half adder have a carry,
then it will be neglected it and adds only the A and B bits. That means the binary
addition process is not complete and that’s why it is called a half adder. The truth table,
schematic representation and XOR//AND realization of a half adder are shown in the
figure below.
INTRODUCTION

Schematic symbol and truth table of exclusive OR (XOR) gate.
(5 mark)
Explanation of 1-bit half-adder circuit operation. (10mark)
The basic 1-bit half-adder circuits. The sum bit is calculated with XOR gates, while the
AND gates are used to check whether two (or more) inputs are 1, which implies that the
carry out bit must be set.The half adder adds two single binary digits A and B. It has two
outputs, sum (S) and carry (C). The carry signal represents an overflow into the next
digit of a multi-digit addition. The value of the sum is 2C + S. The simplest half-adder
design, pictured on the right, incorporates an XOR gate for S and an AND gate for C. With
the addition of an OR gate to combine their carry outputs, two half adders can be
combined to make a full adder.These are the least possible single-bit combinations. But
the result for 1+1 is 10. Though this problem can be solved with the help of an EXOR
Gate, if you do care about the output, the sum result must be re-written as a 2-bit
output.Here the output ‘1’of ‘10’ becomes the carry-out. The result is shown in a truth-
table below. ‘SUM’ is the normal output and ‘CARRY’ is the carry-out. From the
equation it is clear that this 1-bit adder can be easily implemented with the help of
EXOR Gate for the output ‘SUM’ and an AND Gate for the carry.

1. DESIGN Individual xor GATES
a) Created a new file in L-edit, and saved the file as Half_adder_chong.tdb.
b) Go to cell and then rename cell0 as XOR_gate.
LAB WORK
ACTIVITY

c) In cell ‘XOR gate’, drawn the layout of XOR gate that according to XOR gate
stick diagram in Appendix and then label its.
d) Selected ToolDRC, to ensure that the design does not violating any design
rules.

2. DESIGN Individual AND GATES
a) Open a new cell and renamed it as ‘AND gate’.
b) In cell ‘AND gate’, drawn the layout of 2-input AND gate thataccording to AND
gate stick diagram in Appendix and label it.

c) Selected ToolDRC, to ensure that the design does not violating any design
rules.
3. DESIGN half adder.
a) Open a new cell and renamed it as ‘half adder’.

b) Go to cell, and then Instanced the XOR gate layout and AND gate layout in this
new cell and made connection of these two layouts.
c) Selected ToolDRC, to ensure that the design does not violating any design
rules.

Area: 7.75µm X 21.25µm=164.688 (denote 1lamda=0.125micron)
RESULT OF HALF
ADDER

This lab work will consider the complete half adder layout that based combination of
XOR gate and ANDis presented, which after completing the lab phase, we will be able
to design an individual 2-input logic gates which is AND gate and XOR gate based on
given specification design rule. We had to combine these two gate together to form the
half adder layout.
Initially the design of XORand ANDlayout, we able to recognize schematic circuit, logic
symbols and truth table of XOR gates and AND gate.In half adder lab, we canhad to
design circuits that are capable of performing simple addition with the help of logic gates.
APPENDIX
CONCLUSION

1 77 6 6
8 1010 7 9
VDD
GND
A BA B
4 2 3 5
F
Exclusive-OR (XOR) Stick Diagram
2-input AND gate Stick Diagram
GND
F=A.B
A B
S
S
D D S
VDD
SD SD
2-input NAND gate Inverter
input
VDD
GND
F = A.B

Half adder layout design

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