A transmission gate is similar to a relay that can conduct in both directions or block by a control signal with almost any voltage potential. CMOS transmission gate consists of one nMOS and one pMOS transistor, connected in parallel. The gate voltages applied to these two transistors are also set to be complementary signals. As such, the CMOS TG operates as a bidirectional switch between the nodes A and B which is controlled by signal C.

1. 1
ELECTRONICS CIRCUIT LAB (EEC 752)
REPORT
ON
REALIZATION OF 2:1 MUX USING TG
Submitted for the partial fulfillment of award of the degree of
Bachelor of Technology
Of
Electronics and Communication Engineering
Submitted By
SUMIT KUMAR
1219231105
4th
year ECE, Section B
Under the Guidance of
MR. DHARMENDRA NISHAD
(Asst. Professor)
Deptt. Of ECE
Deptt. Of Electronics and Communication Engineering
G.L. BAJAJ INSTITUTE OF TECHNOLOGY AND MANAGEMENT
Plot No. 2, Knowledge Park III, Gr. Noida
Session: 2015-16

2. 2
Deptt.of Electronics and Communication Engineering
G. L. BAJAJ INSTITUTE OF TECHNOLOGY AND MANAGEMENT
[Approved by AICTE, Govt. of India & Affiliated to U.P.T.U, Lucknow]
CERTIFICATE
Certified that SUMIT KUMAR have carried out the lab project work presented
in this report entitled “REALIZATION OF 2:1 MUX USING TG” for the
award of Bachelor of Technology in Electronics and Communication
Engineering during the academic session 2015-16 from Uttar Pradesh
Technical University, Lucknow. The project embodies result of the work and
studies carried out by Student himself and the contents of the report do not form
the basis for the award of any other degree to the candidate or to anybody else.
(Mr. Dharmender Nishad) (Mr. DHARMENDRA NISHAD)
(Lab Co-ordinator) (Lab Co-ordinator)
(Asst. Professor) (Asst.Professor)
Deptt.of ECE Deptt.of ECE
H. O. D., Deptt.of ECE
Date:

3. 3
ACKNOWLEDGEMENT
I heartily express my gratitude to those who generously helped me in preparing
my report on REALIZATION OF 2:1 MUX USING TG of their knowledge
and experiences.
I would like to thank and pay my obligation to DR. AMIT SEHEGAL, HOD,
ECE DEPTT. I would also like to acknowledge with much appreciation the
crucial role of MR. DHARMENDRA NISHAD (ECE DEPTT.) for her able
guidance, invaluable suggestions, keen interest and her considerable attitude.
I pay special thanks to all my honorable teachers, my parents along with my
classmates who directly or indirectly helped me to accomplish my work.
SUMIT KUMAR
Roll No.: 1219231105
4th year ECE, Section B

4. 4
TABLE OF CONTENTS
CHAPTER NO. TITLE PAGE NO.
TITLE PAGE AND COVER PAGE i
CERTIFICATE ii
ACKNOWLEDGEMENT iii
TABLE OF CONTENTS iv
LIST OF FIGURES v
ABSTRACT 1
1. INTRODUCTION 3
1.1 Y-CHART 6
2. BEHAVIOUR 7
3. STRUCTURE 9
4. SIMULATION 12
4.1 INTRODUCTION TO PSpice 12
4.2 TYPES OF ANALYSIS 14
4.3 LIMITATION 16
4.4 SIMULATION OF TRANSMISSION GATE 17
4.5 SIMULATION OF CMOS INVERTER 18
4.6 SIMULATION OF 2:1 MUX 20
5. CONCLUSION 23
REFERENCES 27

5. 5
LIST OF FIGURES
FIGURE NO. TITLE PAGE NO.
1.2:1 MUX ……………………………………………………………01
2. 2:1 MUX TRUTH TABLE….….…………………………………..01
3. 4:1 MUX AND 8:1 MUX..………………………………………....04
4. BASIC DESIGN STEPS IN VLSI ………………………………...05
5. Y-CHART…………………...…………………..………................06
6. 8:1 MUX…………………………………………………………....07
7. TRUTH TABLE OF 8:1 MUX………..……………………..…......08
8. IMPLEMENTATION OF 8:1 MUX USING 2:1 MUX..........…......09
9. IMPLEMANTATION OF 2:1 MUX USING TG ……………........09
10. TRANSMISSION GATE SYMBOL……………………..............10
11. LAYOUT OF TRANSMISSION GATE….....................................10
12. INVERTER……………………………………………..…..........11
13. ORCAD CAPTURE LITE EDITION……………………………15
14. SIMULATION CIRCUIT OF TG ON PSpice…………………...16
15. SIMULATION OUTPUT OF TG ON PSpice…………………...17
16. CIRCUIT OF INVERTER…………………………………….....17
17. SIMULATION CIRCUIT OF INVERTER ON PSpice…………18
18. SIMULATION OUTPUT OF INVERTER ON PSpice…………18
19. Circuit and Truth Table of 2:1 MUX……………………………..19
20. SIMULATION CIRCUIT OF 2:1 MUX ON PSpice………….....20
21. SIMULATION OUTPUT OF 2:1 MUX USING STEP INPUT…21
22. SIMULATION OUTPUT OF 2:1 MUX USING sine INPUT…...21

6. 6
ABSTRACT
The metal–oxide–semiconductor field-effect transistor (MOSFET) is a type of
transistor used for amplifying or switching electronic signals. The main
advantage of a MOSFET over a regular transistor is that it requires very little
current to turn on (less than 1mA), while delivering a much higher current to a
load (10 to 50A or more). Transistors are used as switches to pass logic levels
between nodes of a circuit, instead of as switches connected directly to supply
voltages. This reduces the number of active devices, but has the disadvantage
that the difference of the voltage between high and low logic levels decreases at
each stage. Each transistor in series is less saturated at its output than at its
input. If several devices are chained in series in a logic path, a conventionally
constructed gate may be required to restore the signal voltage to the full value.
By contrast, conventional CMOS logic switches transistors so the output
connects to one of the power supply rails, so logic voltage levels in a sequential
chain do not decrease.
A transmission gate is similar to a relay that can conduct in both directions or
block by a control signal with almost any voltage potential. CMOS transmission
gate consists of one nMOS and one pMOS transistor, connected in parallel. The
gate voltages applied to these two transistors are also set to be complementary
signals. As such, the CMOS TG operates as a bidirectional switch between the
nodes A and B which is controlled by signal C. If the control signal C is logic-
high, i.e., equal to VDD, then both transistors are turned on and provide a low-
resistance current path between the nodes A and B. If, on the other hand, the
control signal C is low, then both transistors will be off, and the path between
the nodes A and B will be an open circuit. This condition is also called the high-
impedance state.

7. 7
Pass transistor logic often uses fewer transistors, runs faster, and requires less
power than the same function implemented with the same transistors in fully
complementary CMOS logic. The designers of the Z80 and many other chips
save a few transistors by implementing the XOR using pass-transistor logic
rather than simple gates.
Transmission Gate Applications are Mux XOR D Latch D Flip Flop.
MULTIPLEXER CIRCUIT is a circuit that generates an output that exactly
reflects state of one of a number of data inputs, based on value of one or more
control inputs is called “multiplexer”. A multiplexer with two data inputs is
referred as “2-to-1 or 2:1” multiplexer. A multiplexer of 2n inputs has n select
lines, which are used to select which input line to send to the output.
Multiplexers are mainly used to increase the amount of data that can be sent
over the network within a certain amount of time and bandwidth. A multiplexer
is also called a data selector. An electronic multiplexer makes it possible for
several signals to share one device or resource, for example one A/D converter
or one communication line, instead of having one device per input signal.

8. 8
CHAPTER 1
INTRODUCTION
In principle, a transmission gate made up of two field effect transistors, in
which - in contrast to traditional discrete field effect transistors - the substrate
terminal (Bulk) is not connected internally to the source terminal. The two
transistors, an n-channel MOSFET and a p-channel MOSFET are connected in
parallel with this, however, only the drain and source terminals of the two
transistors are connected together. Their gate terminals are connected to each
other via a NOT gate (inverter), to form the control terminal.
Two variants of the "bow tie" symbol commonly used to represent a
transmission gate in circuit diagrams.
As with discrete transistors, the substrate terminal is connected to the source
connection, so there is a transistor to the parallel diode (body diode), whereby
the transistor passes backwards. However, since a transmission gate must block
flow in either direction, the substrate terminals are connected to the respective
supply voltage potential in order to ensure that the substrate diode is always
operated in the reverse direction. The substrate terminal of the p-channel
MOSFET is thus connected to the positive supply voltage potential and the
substrate terminal of the n-channel MOSFET connected to the negative supply
voltage potential.
In digital circuit design, the selector wires are of digital value. In the case of a
2-to-1 multiplexer, a logic value of 0 would connect 𝑖0 to the output while a
logic value of 1 would connect 𝑖1 to the output. In larger multiplexers, the
number of selector pins is equal to log2(𝑛) where n is the number of inputs. For
example, 9 to 16 inputs would require no fewer than 4 selector pins and 17 to

9. 9
32 inputs would require no fewer than 5 selector pins. The binary value
expressed on these selector pins determines the selected input pin.
A 2-to-1 multiplexer has a Boolean equation where 𝐴 and 𝐵 are two inputs 𝑠 is
the selector input and 𝑧 is output.
𝑧 = (𝐴. 𝑆′
) + (𝐵. 𝑆)
Fig.1 2:1 MUX Fig.2 2:1 MUX TRUTH TABLE
A multiplexer is a combinational circuit that selects binary information from
one of the many input lines and directs it to a single output line. Therefore,
apart from the input lines and the output line, selection lines are used that
selects a particular input line. The multiplexer is basically a data selector
analogous to an electronic switch that selects one of the multiple sources.
Fig.3 4:1 and 8:1 MUX

10. 10
Here, 4:1 and 8:1 MUX have been shown, in 4:1 MUX there are 2 select lines
and 8:1 MUX have 3 select lines i.e. MUX have log2(𝑛) select lines where n
are the input lines present in MUX.
Designing of any Electronic Circuit goes through following steps:
Fig.4 BASIC DESIGN STEPS IN VLSI
This is the top down approach in which problem is divided from sub steps
simplifying the problem with each step and with each step more and more
information revealed by the method about the problem. Above is the Design
Flow diagram help in designing the Digital circuits. A good representation of
Design flow can be achieved through Y-Chart also:

11. 11
1.1 Y- CHART:
Fig.5 Y-CHART
Designing of 8:1 MUX can be approached through:
Now we will describe the Designing methods step by step:

12. 12
CHAPTER 2
BEHAVIOR
8:1 multiplexer is a combination circuit which can be describe in digital form
using Boolean expression and Truth Table.
Fig.6 8:1 MUX
Here, 𝐼0, 𝐼1, 𝐼2, 𝐼3, 𝐼4, 𝐼5, 𝐼6, 𝐼7 are inputs to the MUX and 𝑠0, 𝑠1, 𝑠2 are the 3 select
lines of the MUX and 𝑂𝑢𝑡 is the output of the MUX.
8:1 multiplexer is a combination circuit which can be describe in digital form
using Boolean expression and Truth Table.
𝑂𝑢𝑡 = 𝑠2
′
𝑠1
′
𝑠0
′
𝐼0 + 𝑠2
′
𝑠1
′
𝑠0 𝐼1 + 𝑠2
′
𝑠1 𝑠0
′
𝐼2 + 𝑠2
′
𝑠1 𝑠0 𝐼3 + 𝑠2 𝑠1
′
𝑠0
′
𝐼4
+ 𝑠2 𝑠1
′
𝑠0 𝐼5 + 𝑠2 𝑠1 𝑠0
′
𝐼6 + 𝑠2 𝑠1 𝑠0 𝐼7
𝐼0 𝐼1 𝐼2 𝐼3 𝐼4 𝐼5 𝐼6 𝐼7 𝑠0 𝑠1 𝑠0 𝑂𝑢𝑡
0/1 0/1 0/1 0/1 0/1 0/1 0/1 0/1 0 0 0 𝐼0
0/1 0/1 0/1 0/1 0/1 0/1 0/1 0/1 0 0 1 𝐼1
0/1 0/1 0/1 0/1 0/1 0/1 0/1 0/1 0 1 0 𝐼2
0/1 0/1 0/1 0/1 0/1 0/1 0/1 0/1 0 1 1 𝐼3

13. 13
0/1 0/1 0/1 0/1 0/1 0/1 0/1 0/1 1 0 0 𝐼4
0/1 0/1 0/1 0/1 0/1 0/1 0/1 0/1 1 0 1 𝐼5
0/1 0/1 0/1 0/1 0/1 0/1 0/1 0/1 1 1 0 𝐼6
0/1 0/1 0/1 0/1 0/1 0/1 0/1 0/1 1 1 1 𝐼7
Fig.7 TRUTH TABLE OF 8:1 MUX

14. 14
CHAPTER 3
STRUCTURE
Structure level is the most important level in designing of the Digital circuit, it
is recommended to design as much possible at this level, helps in subsequent
designing of levels.
8:1 multiplexer can be implemented using 2:1 MUX.
Fig.8 IMPLEMENTATION OF 8:1 USING 2:1
2:1 Mux can be implemented using Transmission Gate and a inverter logic:
Fig.9 IMPLEMANTATION OF 2:1 MUX USING TRANSMISSION GATE

15. 15
Transmission Gate and Inverter can be implemented through Transistor:
Fig.10 TRANSMISSION GATE
Fig.11 LAYOUT OF TRANSMISSION GATE

16. 16
This is the CMOS Transmission gate having A as input and B as output using
two MOSFET and act as a switch controlled by C signal.
Fig12. INVERTER
This is the Inverter Logic which inverts the input signal. This is also a CMOS
circuit.

17. 17
CHAPTER 4
SIMULATION
Simulation can be done using the PSpice OrCAD capture Software suit. We
will simulate the each step of the MUX i.e. first we simulate transmission gate
then inverter then 2:1 Mux using transmission gate and at last we will simulate
the 8:1 MUX using transmission gate.
For simulation, in simulation setting we used time domain (Transient) as
analysis type
4.1 INTRODUCTION TO PSPICE
SPICE (Simulated Program with Integrated Circuit Emphasis) is a general
purpose software that simulates different circuits and can perform various
analysis of electrical and electronic circuits including time domain response,
small signal frequency response, total power dissipation, determination of nodal
voltages and branch current in a circuit, transient analysis, determination of
operating point of transistors, determinations of transfer functions etc. This
software is designed in such a way so that it can simulate different circuit
operations involving transistors, operational amplifiers (op – amp) etc. and
contains models for circuit elements (passive as well as active).
SPICE was first developed in the University of California, Berkeley, USA in
the early 1970s. Subsequently an improved version SPICE 2 was available in
the mid1970s especially to support computer aided designs. In due course of
time this program (SPICE 2 has become so versatile in the industry that people
used to call, this program itself as SPICE. PSpice is also the member of SPICE
family and it is a commercial software product based on SPICE algorithm. It is
useful for simulating all types of circuits in a variety of applications. In both

18. 18
SPICE and PSpice, the circuit is described by statements those are stored in a
file (namely Circuit File).
The SPICE simulator is assigned to read this file to run the simulation. In
PSpice, the statements are self – contained and independent; obviously they do
not interact with each other. The statements are also easy to learn and use.
PSpice includes additional features that make the program more flexible and
user friendly. Notably among other features is the graphics postprocessorprobe
which acts like a software oscilloscope and is capable of exhibiting various
waveforms. PSpice has become one of the most popular circuit simulation
programs. In order to draw the circuit and create a schematic file, schematic
editor can be used in the PSpice simulation.
PSpice is a part of larger software package called the Design Lab, originally
developed by MicroSim Corporation as the Design Centre. It is now marketed
by OrCAD.
PSpice was the first version of UC Berkeley SPICE available on a PC, having
been released in January 1984 to run on the original IBM PC. This initial
version ran from two 360 KB floppy disks and later included a waveform
viewer and analyser program called Probe. Subsequent versions improved on
performance and moved to DEC/VAX minicomputers, Sun workstations, Apple
Macintosh, and Microsoft Windows.
Version 3.06 was released in 1988, also came on two 5.25 floppy discs, and had
a "Student Version" available which would allow a maximum of up to ten
transistors to be inserted.
4.2 TYPES OF ANALYSIS
The type of simulation performed by PSpice depends on the source
specifications and control statements. The analyses usually executed in PSpice
are listed below.
DC Analysis

19. 19
It is used for circuits with time–invariant sources (e.g. steady-state dc sources).
It calculates all nodal voltages and branch currents over a range of values. The
types of dc sweep analyses and their corresponding. (Dot) commands are
described below:
• Linear sweep: .DC [LIN] <sweep variable name> <start value> <end
value> <increment value>
• Logarithmic sweep: .DC <DEC|OCT> <sweep variable name> <start
value> <end value> <points value>
• Sweep over List of values: .DC <sweep variable name> LIST <value>*
All these sweep types can also be nested by adding another set of parameter
name and values at the end.
Transient Analysis
It is used for circuits with time variant sources (e.g., sinusoidal
sources/switched dc sources). It calculates all nodes voltages and branch
currents over a time interval and their instantaneous values are the outputs. The
corresponding. (Dot) command is as follows:
.TRAN <print step value> <final time value> [no-print value [step ceiling
value]] [SKIPBP]
AC Analysis
It is used for small signal analysis of circuits with sources of varying
frequencies. It calculates the magnitudes and phase angles of all nodal voltages
and branch currents over a range of frequencies. The corresponding. (dot)
command is as follows: .
AC <LIN|DEC|OCT> <Number of points> <Start frequency value> <End
frequency value>

20. 20
Fig13. ORCAD CAPTURE LITE EDITION
4.3 LIMITATIONS
PSpice has the following limitations:
• The student (free) version of PSpice is restricted to analyses circuits up to
10 transistors only.
• PSpice does not support an iterative method of solution.
• The circuit cannot be analyzed for various component values without
editing program statements. Hence, the program is not interactive.
• The input impedance cannot be determined directly without running the
graphic post processor, Probe.
• The output impedance of a circuit cannot be printed or plotted directly.
• Distortion analysis is not possible.

21. 21
To realize the circuit we can approach to two methods one is making library file
of transmission gate and inverter second by simply adjoining transistor as per
the circuit diagram.
4.4 SIMULATION OF TRANSMISSION GATE-:
We can simulate the circuit of transmission gate by having the circuit:
Fig14. SIMULATION CIRCUIT OF TG ON PSpice
Here, we have connected nMOS and pMOS parallel to each other control signal
is applied to the gate of MOS. Input is at Drain and Source is our output.
Whenever the control signal is at low the output will be high and whenever
control signal is high the output will be low, acting as a switch.
Simulation output is shown here:

22. 22
Fig15. SIMULATION OUTPUT OF TG ON PSpice
Red line is showing the Control signal and Green line is output. Here, +5 is high
and 0 is low.
4.5 SIMULATION OF CMOS INVERTER:
CMOS Inverter can be simulating by connecting two transistors in series, pair
of switches are operated in a complementary fashion by the input voltage.
Fig16. CIRCUIT OF INVERTER
This circuit converts the high level logic of input into low level of output and
low level input to high level output.

23. 23
Fig17. SIMULATION CIRCUIT DIAGRAM OF INVERTER ON PSpice
Fig18. SIMULATION CIRCUIT DIAGRAM OF INVERTER ON PSpice

24. 24
4.6 SIMULATION OF 2:1 MUX:
Simulation of 2:1 can be simulating in PSpice using inverter and transmission
gate. We require two transmission gate and one inverter circuit. The structural
level of circuit can be representing like:
Fig.19 Circuit and Truth Table of 2:1 MUX

25. 25
PSpice circuit model can be shown like:
Fig20. SIMULATION CIRCUIT OF 2:1 MUX ON PSpice
Input and select line for the 2:1 MUX input is:
Fig21. SIMULATION OUTPUT OF 2:1 MUX ON PSpice USING STEP INPUT

26. 26
Output for the sine wave input:
Fig22.SIMULATION OUTPUT OF 2:1 MUX ON PSpice USING sine wave INPUT

27. 27
CHAPTER 5
CONCLUSION
In this paper, different multiplexers have been implemented, simulated,
analyzed and compared. Using driving capability technique this problem can be
minimized. The conventional CMOS style based designs have great output
voltage level and less noise margin. Though they suffer higher delay and
consume large area these designs can be considered for accurate and reliable
output. Transmission gate based designs consumes high power. But the main
drawback is that there is no selection pin, so these designs are not appropriate
for multiplexing where both the inputs may have identical value at any instant.
This study was made possible with the help of the Simulation and VLSI LAB.

28. 28
REFRENCES
http://iosrjournals.org/iosr-jvlsi/papers/vol3-issue6/D0361727.pdf
http://webpages.eng.wayne.edu/cadence/ECE6570/doc/lect3_1.pdf
http://ir.lib.cyut.edu.tw:8080/bitstream/310901800/9952/1/10-6.pdf
http://research.ijcaonline.org/volume99/number5/pxc3897911.pdf
https://courseware.ee.calpoly.edu/~dbraun/courses/ee307/W02/02_03/02_03
.html
http://iitg.vlab.co.in/?sub=59&brch=165&sim=904&cnt=1
http://www.ijser.org/paper/A-New-High-Speed-Low-Power-12-Transistor-
Full-Adder-Design-with-GDI-Technique.html
http://www.cmccord.co.uk/Downloads/4thYear/VLSI.pdf
http://gatedesignsnorit.blogspot.in/2015/06/design-xor-gate-using-mux.html
http://gatedesignsnorit.blogspot.in/2015/05/design-nand-gate-using-
mux.html