A Mini Project Report on

A Three Stage Comparator and Its Modified Version With High Speed
and Low Kickback
Submitted in partial fulfillment for the award of the degree of Bachelor of Technology in

Electronics and Communication Engineering by

Tellagorla Pavani 21321A0488

Palamuru Pooja 21321A0489

Under the esteemed Guidance of

Internal Guide

Ms. Radhika Ravikrindhi

Assistant Professor, ECE Department

Bhoj Reddy Engineering College for Women

Department of Electronics and Communication Engineering
(Sponsored by Sangam Laxmibai Vidyapeet, approved by AICTE & affiliated to JNTUH)
Vinaynagar, Santoshnagar X roads, Saidabad, Hyderabad – 500 059
Ph: +91-40-2459 2400 Fax: +91-40-2453 7281, www.brecw.ac.in, principal@brecw.ac.in
 CERTIFICATE

2024-25
This is to certify that the Mini Project Report entitled “A Three Stage Comparator
and Its Modified Version With High Speed Low Kickback” is a bonafide work
carried over by Ms. Tellagorla Pavani (21321A0488), Ms. Palamuru Pooja
(21321A0489) in partial fulfillment of the requirements for the award of the degree
Bachelor of Technology in Electronics and Communication Engineering from Bhoj
Reddy Engineering College for Women, Hyderabad, affiliated to Jawaharlal Nehru
Technological University Hyderabad (JNTUH) during the Third Year Second
Semester of B. Tech course (academic year 2023-2024).

Ms Radhika Ravikrindhi S Manjula

Internal Guide HOD-ECE

External Examiner
Sangam Laxmibai Vidyapeet is an educational society for promotion of education among girls and
women. It is established in 1952 and registered under the Telangana Societies Registration Act
 Acknowledgment
The satisfaction that accompanies the successful completion of the task would
be incomplete without the mention of the people who made it possible, whose constant
guidance and encouragement crown all the efforts with success.

I would like to express my sincere gratitude to Ms. Radhika Ravikrindhi,

Assistant Professor and Project guide for the eminent guidance and supervision at
every stage.

I am thankful to Ms. S Manjula, Head of the Department, for her valuable

guidance and encouragement during my project.

I also thank Dr. J Madhavan, Principal, BRECW for providing a wonderful

education environment in our college.

I am equally thankful to Dr. K Ashok Kumar, Project Coordinator for his

continuous support and all the staff of the Electronics and Communication Engineering
Department of BRECW for their timely help and suggestions in the Project.

Tellagorla Pavani(21321A0488) tellagorlapavani@gmail.com

Palamuru Pooja(21321A0489) poojapalamuru@gmail.com

 Table of Content

Particulars Page Number

List of Figures i
Abstract ii
Chapter 1 Introduction 1
1.1 Introduction 1
1.2 Aim of the Project 1
1.3 Motivation 2
1.4 Objectives 2
1.5 Organization of the Report 2
1.6 Literature Survey 2
1.7 Conclusion 4
Chapter 2 Software Requirements 5
2.1 Introduction 5
2.2 Software Requirements 5
2.3 Technologies used (EDM) 5
2.4 Conclusion 14
Chapter 3 Three stage comparator and its modified version 15
3.1 Introduction 15
3.2 Existing System 15
3.3 Proposed System 18
3.4 Conclusion 20
Chapter 4 Advantages, Disadvantages and Applications 21
4.1 Advantages 21
4.2 Disadvantages 22
4.3 Applications 23
Chapter 5 Results and Discussion 24

5.1 Introduction 24
 5.2 Working 27

5.3 Results 28
5.4 Conclusion 28
Chapter 6 Conclusion and Future scope 29
6.1 Conclusion 29
6.2 Future Scope 30
References
 List of Figures

Figure Title Page Number

2.1 Schematic of Windo of SEDIT 6
2.2 NMOS Schematic entry 7
2.3 NMOS Schematic entry on Window 8
2.4 Voltage Source Entry 9
2.5 Voltage DC Source Component Entry 10
2.6 Wire Entry 10
2.7 Net Entry 11
2.8 Schematic Entry Od NMOS 11
2.9 V-I Characteristics 13
2.10 TSPICE Report 13
2.11 Simulation Result of Inverter 14
3.1 Miyahara’s two-Stage Comparator 16
3.2 Three-Stage Comparator in this Work 17
3.3 Proposed Modified Version 18
5.1 Schematic of Modified Three-stage 25
5.2 Comparator 26
5.3 Proposed Schematic of Three-Stage 27
5.4 Comparator 28

i
 Abstract
The manuscript delves into the design of digital decoders, specifically focusing on the 4
×16 and 3 × 8 decoders. It examines the use of 2 × 4 decoders and different logic gates in the
design process. Additionally, it explores the implementation of a 4 × 16 decoder using a 3 × 8
decoder and CMOS technology, known for its efficient power usage and fast performance. This
study examines power consumption in different architectural configurations, with a specific focus
on CMOS-based decoder implementation. The authors adeptly employ Cadence Virtuoso software
for circuit realization and evaluation. Power consumption attributes are carefully measured for
each decoder design utilizing CMOS technology as the framework. The empirical findings are
used as the basis for a thorough comparative analysis, examining the complex connection between
circuit architecture and power efficiency. The analysis offers valuable insights for selecting
decoders wisely, aiding circuit designers in finding architectures that strike a balance between
energy efficiency and uninterrupted operation. Furthermore, it offers a comprehensive insight into
power consumption dynamics, contributing to the scholarly community's understanding of
energy-efficient digital circuitry. The study has the potential to drive innovation and efficiency in
CMOS-based decoding circuits as the field advances.
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Chapter 1
Introduction
1.1 Introduction
In the critical area of digital decoder design, the optimization of power consumption
and performance takes center stage. The study focuses on the intricate architectures of two
vital decoder types: the 4 × 16 decoder and the 3 × 8 decoder. These decoders are integral
components of digital systems, requiring meticulous design to achieve operational efficiency.
The research explores using smaller 2 × 4 decoders as building blocks and investigates various
logic gate configurations, offering a modular and hierarchical approach to circuit design. A
key aspect of this inquiry is the implementation of a 4 × 16 decoder using a 3 × 8 decoder,
demonstrating innovative architectural strategies that improve scalability and adaptability.

1.2 Aim of the Project

Digital decoders are fundamental components in modern digital systems, widely used
in applications such as memory addressing, data demultiplexing, and communication
systems. As the demand for high-speed and low-power digital circuits grows, the design of
power-efficient Complementary Metal-Oxide-Semiconductor (CMOS)-based decoders has
become a critical area of research. This document focuses on the design, optimization, and
implementation of a power-efficient CMOS-based digital decoder, addressing key challenges
and strategies to minimize power consumption while maintaining performance and reliability.

1.3 Motivation
The rapid growth of digital technology has increased the demand for power-
efficient circuits, especially in battery-operated and high-performance computing
devices. As semiconductor technology scales down, power dissipation has become a
major concern in Very Large-Scale Integration (VLSI) design. Digital decoders, being
fundamental components in digital circuits, contribute significantly to overall power
consumption. This project is motivated by the need to develop low-power CMOS-based
digital decoders that optimize energy efficiency without compromising performance and
reliability.

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1.4 Objectives
The primary objective of this project is to design and implement a power-efficient
CMOS-based digital decoder while optimizing its performance and reliability. The focus is
on minimizing power consumption by employing advanced low-power design techniques
such as clock gating, power gating, and transistor sizing* to reduce dynamic and static power
dissipation. The project aims to balance key performance metrics, including power, delay, and
area (PDA), ensuring that the decoder operates efficiently without compromising speed or
functionality. Additionally, the study will explore and compare different **low-power logic
architectures, such as pass-transistor logic (PTL), transmission gate logic (TGL), and
adiabatic logic, to determine the most effective design strategy. A comparative analysis
between traditional CMOS decoders and optimized low-power architectures will be
conducted to evaluate power savings and performance improvements. The proposed design
will be implemented and simulated using industry-standard EDA tools (such as Cadence,
Synopsys, or Tanner) to validate its efficiency, making it suitable for applications in memory
addressing, microprocessors, and embedded systems.

1.5 Organization of the Report

This report is structured to provide a comprehensive understanding of the design
and implementation of a power-efficient CMOS-based digital decoder. Each chapter
presents key aspects of the project, from fundamental concepts to design methodologies,
simulation results.

This provides an overview of the project, highlighting the importance of power-

efficient digital decoders, the motivation behind the study, and the key objectives. It also
outlines the scope of the research and its significance in modern digital system design.

This section explores existing work on CMOS-based digital decoders, power

reduction techniques, and various design methodologies. It discusses different low-power
logic styles, previous research findings, and the challenges associated with power-
efficient decoder design.

This chapter details the proposed design approach, including the selection of
CMOS technology, logic minimization techniques, and circuit optimizations for reducing
power consumption. It also explains the simulation setup, tools used (such as Cadence,
Synopsys, or Tanner), and design validation techniques. This section presents the

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implementation of the proposed decoder design, including circuit schematics, layout
design, and power analysis. Simulation results are discussed, comparing power
consumption, delay, and area with conventional decoder architectures.

This chapter provides an in-depth analysis of the simulation results, evaluating

the effectiveness of the implemented low-power techniques. Trade-offs between power,
performance, and area are analyzed, along with comparisons to existing decoder designs.

1.7 Conclusion
In this project, a power-efficient CMOS-based digital decoder was designed and
implemented to address the increasing demand for low-power digital circuits. Various power
reduction techniques, such as clock gating, power gating, transistor optimization, and logic
minimization, were applied to reduce both dynamic and static power dissipation. The
proposed design was simulated using industry-standard EDA tools, and the results
demonstrated significant improvements in power efficiency compared to conventional CMOS
decoder architectures.

For future work, further improvements can be explored, such as the integration of
emerging low-power technologies, advanced fabrication techniques, and adaptive power
management strategies. Additionally, implementing machine learning-based optimization
techniques can help refine power-efficient decoder designs even further. The insights gained
from this study pave the way for more sustainable and high-performance digital circuit
designs in modern electronics.

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Chapter 2
Literature Survey
2.1 Introduction
2.2 Software Requirements
Mentor Graphics, now part of Siemens, offers a comprehensive suite of Electronic Design
Automation (EDA) tools that are widely used in the semiconductor and electronics industry.
These tools assist engineers in all stages of electronic design, from conceptualization and
simulation to layout, verification, and manufacturing. When preparing a report, particularly
on complex circuits like a three-stage comparator and its modified version with enhanced
speed and low kickback noise, Mentor Graphics tools provide the necessary functionality for
accurate design and performance analysis.

2.3 Technologies used(EDM):

Tanner EDA is a suite of tools for the design of integrated circuits. These tools allow you to
enter schematics, perform SPICE simulations, do physical design (i.e., chip layout), and
perform design rule checks (DRC) and layout versus schematic (LVS) checks. There are 3
tools that are used for this process: S-edit - a schematic capture tool T-SPICE - the SPICE
simulation engine integrated with S-edit L-edit - the physical design tool.Using S-Edit
(Schematic Entry Tool) & T-SPICE (Analog Simulation Tool).

Curves of an NMOS Transistor S-edit is a schematic entry tool that is used to document
circuits that can be driven forward into a layout of an integrated circuit. It also provides the
ability to perform SPICE simulations of the circuits using a simulation engine called T-SPICE.
T-SPICE can be setup and invoked from with in S-edit. Part 1: Setup your Directory Structure
& download Libraries:
a) Log onto a computer on 6th floor Cobleigh.
b) You want to create a directory for all of your Tanner EDA projects. You also will need
to download and unzip a set of library & model files from the course website that will be used
for your simulations. - Create a directory structure named “EELE414_VLSI_Fall2011\Tanner
Projects.

c) Go to the course website and download the zip file called “Tanner_Libraries.zip”. Unzip
it into your Tanner Projects directory. This group of files contain the necessary information

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to enter components into S-edit (circuit symbols), perform SPICE simulations (models),
and do physical layout (layer definitions, DRC, LVS).

2.3.1 Start a New Design & Setup Libraries

a) Start S-Edit: Start – All Programs – Tanner EDA – Tanner Tools v12.6 – S-Edit v12.6.

b) Start a New Design: Using the pull down menus, create a new design: - File – New - New
Design A dialog will appear asking for a design name and location. When you give the
name, Sedit will create a folder of that name in the directory that you provide that will
contain all of the design files. You should give a descriptive name that represents each
simulation you will be running. - Enter the name “HW03_NMOS_IV_Part1” and browse
to your “EELE414_VLSI_Fall2011\Tanner_Projects ” directory - Click “OK”.

c) Create a new Cell A “cell” is a design element. A cell can contain multiple views such as
schematics and symbols. Cells can be instantiated in other cells. When performing a
simulation, we will typically call the cell “TOP”. When we are testing a circuit, for example
an inverter, the inverter will have its own cell that contains a schematic of the devices and
a symbol. The inverter cell is instantiated in the TOP cell that contains ideal elements such
as voltage sources and probes that are only used for simulation. This allows us to separate
the cells that are actually going to be implemented on the die versus cells that are only used
for simulation. Using the pull down menus, create a new cell view: - Cell – New View: -
enter the cell name “TOP”. Ensure the design name is “HW03_NMOS_IV_Part1” and click
OK. You can leave the interface and view names “view0”. A blank schematic page will
appear. It is a good idea to save this right now.
d) Enter the symbol libraries: First, you need to include a library which contains the symbols
for all basic circuit elements such as resistors, NMOS, capacitors, etc… The libraries for
all the basic symbols are in the Tanner_Libraries.zip file you downloaded and unzipped. -
On the left side of the S-edit screen you’ll see a Libraries window, click on the “Add”
button appear:

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Fig 2.1: Schematic of window of SEDIT

2.3.1 Enter the Schematic to simulate the IV behavior of an NMOS Transistor

Fig 2.2: NMOS Schematic entry

a) Enter the NMOS transistor - On the left, click on “Devices” in the upper window. This will
display all of the symbols available in this group. You should see all of the components
that you can implement on a CMOS integrated circuit. - On the bottom left window, click
once on “NMOS”. You should see the symbol of the NMOS transistor show up in the
symbol viewer window at the bottom. - To place the NMOS, you will click on the
“Instance” button. Two things happen when you click on this button. First, a dialog will
appear that will allow you to setup the parameters for the NMOS. Second, the symbol will

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attach to your mouse. We will place the NMOS in the schematic first and then set its
properties later. This is an easier way to enter the device. Click in the schematic window
to drop an instance of the NMOS. Hit the “Esc” button to end the insert-mode.

Fig 2.3: NMOS Schematic entry

The NMOS is now in the schematic. A note on zooming: - [Home] = zoom fit - [-] =
zoom out - [=] = zoom in - the scroll wheel also zooms in/out. - To setup the NMOS, click on
the NMOS symbol. You will see the properties of the device on the left. We want to setup the
following: - Model : enter “NMOS”. This model is found in the Generic_025 library you
added - Name: M1. The SPICE designation for MOS transistors is to have the name start with
an “M”. S-edit automatically appends an M to the name is the final name will be “MM1” in
the TOP.sp file. But it is good practice to name all MOS transistors with M’s. - W Set to 2.5u.
This is the default. - L Set to 0.25u. This is the default. b) Enter a DC source for VGS - Using
the same process you used for the NMOS symbol, enter a “SPICE_Elements:VoltageSource”.
This is a generic voltage source symbol that is configured as a DC, TRAN, PWL, etc.. in its
properties dialog. - Click on the voltage source and enter the following: - MasterInterface:
DC (this is the default but this is how you would change it to something else. - Name:
VGS_Source (it is a good idea to use descriptive names) - V This is where you will set
the DC voltage (i.e., 4v, 5v). However, for this example we will use a parameter instead of a
hardcoded value. We will enter a parameter name here and then set up the parameter later.
Enter “VGS_param” for the value of V. When performing a DC sweep, you must use
parameters for the sweep. c) Enter a DC source for VDS - Using the same process as above,

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enter a DC source for VGS with the following: - MasterInterface: DC (this is the default but
this is how you would change it to something else. - Name: VDS_Source - V “VDS_param”
Position the sources as in the following figure:

Fig 2.4: Voltage source entry

A note on zooming: - Hold down ALT-M to move a component. While holding these buttons
down, click and drag the components. - To rotate, click on the device and click the [r] button.

The three-stage comparator consists of a pre-amplifier stage, latch stage, and output buffer
stage. Despite its advantages, the conventional three-stage comparator suffers from high
propagation delay and significant kickback noise.

a) Enter Grounds - Using the same process as above, enter 3 grounds from Misc:Gnd

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Fig 2.5: Voltage DC source components entry

b) Enter Wires - You can enter wires by clicking on the “wire” icon at the top

Fig 2.6: Wire entry

Enter wires by clicking on a symbol node and then dragging. Enter corners by clicking once
where you want to turn. - You can label nets using the “Net Label” icon at the top

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Fig 2.7: Net entry

Fig 2.8: Schematic entry of NMOS

2.3.2 Setup the SPICE DC Sweep Analysis

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Using the pull down menus:

Setup – SPICE Simulations

On the left, click on “DC Sweep Analysis”

On the right, enter the following for Source (this is what will be swept)

Source or Parameter Name: VDS_param

Start Value: 0

Stop Value: 2.5 Step: 0.1 Sweep Type: lin

On the right, enter the following for Source (this is what will be swept) source or Parameter

Name: VGS_param

Start Value: 1

Stop Value: 1.5 Step: 0.5 Sweep Type: lin

2.3.3 Simulate the Design

a) First, check you design using the pull down menus:

Tools – Design Checks (any warnings or errors will be shown at the bottom)

b) Simulate your design:

Clock on the Green Arrow to start the simulator:

The T-Spice window will appear. If everything is OK, the waveform viewer will also appear.

If everything worked, your waveforms should look like this:

Setup – SPICE Simulations

On the left, click on “DC Sweep Analysis”

On the right, enter the following for Source (this is what will be swept)

Source or Parameter Name: VDS_param

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Fig 2.9: V-I Characteristics

c) View the Netlist:
In the T-spice window, right click on the file at the bottom and select “Show Netlist” This will
bring up the TOP.sp Netlist that was created and used by the spice engine. This is a good place
to look when you get errors. This is the text based description of what you entered in S-edit.

Fig 2.10: TSPICE report

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d) View the Waveform: - If the windows viewer did NOT automatically appear, you can click
on the file in the Tspice window and select “Show Waveform”

2.3.4 Simulate the Design Graph:

a) First, check you design using the pull down menus:

b) Tools – Design Checks (any warnings or errors will be shown at the bottom)
c) Simulate your design:
Clock on the Green Arrow to start the simulator:
The T-Spice window will appear. If everything is OK, the waveform viewer will also appear.
If everything worked, your waveforms should look like this:

Fig 2.11: Simulation results of inverter

2.4 Conclusion
In conclusion, mentoring in graphic EDA tools is a powerful approach to developing
skilled data professionals who can unlock the full potential of data through effective
analysis and visualization. Organizations that prioritize mentorship not only enhance
their analytics capabilities but also foster a collaborative and innovative work
environment.

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Chapter 3
Software Requirements
3.1 Introduction
Electronic Design Automation (EDA) encompasses a wide range of tools used for designing
and manufacturing electronic systems. Often referred to as ECAD (Electronic Computer-
Aided Design), these tools streamline the design process for system and packaging levels.
The Cadence System Connectivity Manager (SCM) is an industry-standard tool for system-
level design, while Design Entry HDL organizes schematic information, and Cadence PCB
Designer offers a scalable PCB design solution. Validation is carried out by generating test
cases based on a company’s unique design steps or Cadence Change Requests (CCRs) from
industry leaders such as QUALCOMM, ERICSSON, IBM, CISCO, and HP*. Since these
CCRs relate to yet-to-be-launched products, they remain confidential, providing insight into
the complexities of system-level design.

3.2 Software Requirements

These tools enhance testing and debugging skills while improving design concepts across
hardware and software domains. The tools are designed and tested on multiple platforms,
including Linux, Solaris, and Windows XP. Additionally, Tcl scripting is employed to
automate test case generation efficiently, reducing time consumption.

3.2.1 EDA Technology

Printed circuit boards (PCBs) and integrated circuits are only two examples of the many
electronic system components that may be designed and manufactured with the help of
EDA.The ECAD is a typical term for this process.Wire wrap and printed circuit boards both
use the utilization of specialized electronic design automation (EDA) techniques. The tools
collaborate within a design flow utilized by chip designers for the purpose of designing and
analyzing complete semiconductor chips.

The objective of the project is to learn the design flow of System and Packaging level EDA
tools, and to validate the tools for proper functioning. Allegro Design Work bench (ADW)
represents a suite of products that help implement collaborative design environment involving
your design teams, methodologies, corporate design databases, and tools. In addition, you can
use design lifecycle, library development and management, and data management features to
control the design and library management processes.

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The validation is achieved using generation oftest cases ,based on either the company’s own
combination of design steps or based on the CCRs (Cadence Change Requests) filed by the
leading customers which are confidential ,since the end product based on the design issues is
still to be launched in the market. The verification based on these issues not only enhances the
validation skills ,but also provides an insight into the level of complexity at
QUALCOMM,ERICSSON,IBM,CISCO,HPetc work. The scripting language Tcl are used for
making the test case generation and automation tasks more efficient with respect to time
consumption. In this report significant weight age has been given to understand the design
flows of the Cadence Part Developer, Cadence Design Entry HDL and Cadence Database
Editor, Cadence Library Distribution, Cadence Flow Manager based on the company’s
confidential user guides and design workshops..

Electronic Design Automation (EDA) is a specialized field that focuses on the design and
development of integrated circuits (ICs) used in electronics. The utilization of Electronic
Design Automation (EDA) is imperative for chip designers employed in semiconductor
companies. Designing large chips manually is a highly intricate task. The significance of
Electronic Design Automation (EDA) in the field of electronics has witnessed a rapid surge
due to the ongoing advancement and miniaturization of semiconductor technology. There are
two main types of users in the semiconductor industry: foundry operators and design- service
companies. Foundry operators are responsible for operating the semiconductor fabrication
facilities, commonly referred to as "fabs". On the other hand, design-service companies utilize
Electronic Design Automation (EDA) software to assess the manufacturing readiness of
incoming designs.

Electronic Design Automation (EDA) refers to the utilization of computer systems for the
purpose of designing, laying out, verifying, modeling the operation of integrated circuits and
printed circuit boards. The general public tends to primarily direct their attention towards the
final products, with only a moderate level of awareness regarding the internal components
such as chips and circuits. The significance of electronic design automation (EDA) has
experienced a rapid rise due to the ongoing scaling of semiconductor technology. EDA tools
are utilized for the purpose of incorporating programming design functionality into Field-
Programmable Gate Arrays (FPGAs).

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The tools in EDA are divided into two categories:

(a).FE tools (Front End) - This includes tools for system development activities and logic
design activities that encompass logic synthesis, formal checking, and design for test. For
example, Cadence PDV (Part Developer), Cadence Design Entry HDL, Cadence Database
Editor, Cadence Library Distribution, Cadence Flow Manager etc..

(b).BE tools (Back End)-This includes tools for the physical implementation of the logical
designs

3.2.2 Cadence Tools

Cadence Design Systems is a globally recognized leader in the field of EDA technologies
and engineering services. Cadence assists its customers in overcoming obstacles by offering
cutting-edge electronic design solutions that accelerate the development of advanced
integrated circuits and system designs for mass production.The main product

offered by the corporation is software specifically designed for chip and printed circuit board
(PCB) design purposes.

Cadence EDA tool design services are utilized by companies for the purpose of designing,
verifying, and preparing semiconductors and systems for manufacturing. Today, complex
chips go into millions of Set-top boxes, PDAs, cellular phones, and other consumer items,
all designed and brought out under intense cost and time-to-market pressures. Today,
Electronics touches almost every part of our lives, and is ubiquitous, and, is literally changing
everything in and around our lives, for the better. This is truly, the Golden Age of Electronics.
It would have been nearly impossible to design Today's semiconductors and electronic
without electronic design automation (EDA). Electronic Design Automation (EDA) is a
sophisticated and extensively utilized technology that facilitates the Electronics Industry by
managing intricate design complexities. It enables faster time-to-market, enhances
productivity, accuracy, and efficiency.

ompany Profile

Manufacturers cram billions of transistors onto a single chip mobile phones, digital cameras,

computers, and automobile systems need to improve in order to meet the rising expectations
of

today's consumers. The shrinking of transistors and other chip components to sizes smaller
than

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the wavelength of the light required to print them, as a result of the trend toward ever- smaller

process geometries, and this tremendous integration, go hand in hand.

Without electronic design automation (EDA), it would be impossible to develop and

manufacture

Customers that use our technologies can design mobile devices with extended battery lives.
By

utilizing our hardware simulators to execute software on a "virtual" chip long before the
actual

chip is available, designers of ICs for gaming consoles and other consumer electronics can

accelerate time to market. for their products. In order to address manufacturing issues early
in the

design stage, the conventional distance between chip designers and fabrication facilities has
to be

closed. And with the help of our specialized IC design platform, engineers can combine the
best

aspects mixed- signal system-on-chip (SoC) designs that combine the best features of analog
and

digital engineering. These are just some of the many vital Cadence solutions that ensure the

continued success of industry-leading integrated circuits and electronic systems.

manufacturers.

2.4 Market

Products are the primary force behind the world's $1 trillion+ electronics market. aimed at

consumers, is served by Cadence®. Information technology (IT), communications (both

wired

and wireless), and consumer electronics (M&E devices), are some of the key vertical market

categories. More than 90% of the revenue from semiconductors and 75% of the revenue from

electronics equipment are generated globally, respectively.

2.4.1 The major horizontalsegments are:

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1. Silicon providers(including ASIC vendors, foundries, and FPGA ),

2. Systems manufacturers.

3. Semiconductor manufacturers.

In each of these markets, Cadence® is the top supplier of EDA solutions, giving the business

unmatched insight into the electronics design sector.

2.4.2 Two major trends drive electronics design:

1. A rise in silicon production and

2. A convergence of market demands.

Miniaturization is a significant trend as the demand for smaller, more portable electronic
devices

continues to rise. As consumers expect slimmer smartphones, wearable gadgets, and compact

computers, electronic designs are becoming more intricate to fit powerful components into
smaller

spaces. This has led to advances in microchip technology, such as smaller transistors, and
the

integration of multiple functions onto a single chip (System on Chip, or SoC).

Miniaturization not

only enables the creation of sleek devices but also promotes energy efficiency and enhances

portability, making electronics more user-friendly and versatile in various industries.

For more than 30 years, silicon capacity has doubled every 18 to 24 months. Despite the fact
that

Moore's Law is still in effect, productivity limitations are increasingly being pushed, and an
end

appears to be in sight. Electronics companies must continue to invest in order making the
most of

this growing silicon capacity to meet customer expectations for devices that integrate
computing,

communications, and entertainment functions such smartphones, tablets, laptops, desktops,

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Mini Project Report A Three Stage Comparator and Its Modified Version
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televisions, set-top boxes, wireless networks, and cars. To address time-to-market challenges
and

needs for ongoing device functionality evolution, this entails tearing down boundaries
between

the distinct disciplines of PCB design, digital logic, and analog circuits in the present day,
and

embedded software. The only business that combines a broad product offering, subject
knowledge,

and experience with vertical design approach is Cadence®.

2.5 An Overview of Cadence India

Cadence Design Systems biggest research and development center outside the US is located

in located in Noida at Cadence Design Systems (I) Pvt. Ltd. The Cadence creates automation
tools

for the entire range of electronic device and system design., including numerous vital and
popular

technological products. The development of the electronics industry is greatly aided by

Cadence's

presence in India. Additionally, Cadence is developing partnerships with top engineering

schools

in India. Through participation in Cadence India has become an international technology

leader

thanks to its participation in standards-setting forums like the VHDL Initiative towards ASIC

Libraries (VITAL TAG) and the synthesis Inter- operability Working Group (SIWG), both
of

which were founded by VHDL International. VLSI Design and Test (VDAT) is a subset of
the

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Mini Project Report A Three Stage Comparator and Its Modified Version
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Fig 3.1: Miyahara’s two-stage comparator

Although the Miyahara’s two-stage comparator increases the speed, its speed can be further
improved in the following way. As can be seen in Fig. 1, its latch input pair M6–7 are pMOS
transistors, and the pMOS hole mobility is small (2–3 times smaller than the nMOS electron
mobility), limiting the regeneration speed. Thus, our goal is to use nMOS transistors instead
for the latch input pair, so that the regeneration speed could be greatly improved. Meanwhile,
we must maintain the nMOS transistors for the preamplifier input pair. To this end, this brief
presents a three-stage comparator. By adding an extra preamplifier stage, the nMOS input
pairs can be used for both the latch- stage and the first-stage preamplifier, thus improving the
regeneration speed. Besides, these input pairs work in the saturation region at the beginning
of comparison, thus ensuring a small input referred noise. The extra stage of preamplifier also
provides voltage gain, which helps further increase the regeneration speed and suppress the
input referred offset and noise. Compared to the prior three-stage comparator of [12].

The three-stage comparator in this work has a faster speed and a lower input referred noise.
This brief also proposes a modified version of three-stage com- parator. By using a CMOS
input pair at the first-stage preampli- fier, the kickback noise is greatly reduced. An extra path
is also added in the latch stage to further increase the regeneration speed and suppress the
input referred offset and noise. Implemented in the same 130-nm process, the three-stage
comparator in this work increases the speed by 25% compared to the conventional two-stage
comparators, while the proposed modified version improves the speed by 32% and decreases
the kickback noise by ten times.

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Mini Project Report A Three Stage Comparator and Its Modified Version
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Fig 3.2: Three-stage comparator in this work. (a) First two stages (preamplifiers)
(b) Third stage (latch stage)

This improvement is not at the cost of increased input referred offset or noise.
This brief is organized as follows. Section II discusses the three-stage comparator. Section III
analyzes the modified version of three-stage comparator. Section IV shows the simulated and
measured results. Section V concludes the brief.

3.3 Proposed System

In order to reduce the kickback noise and further improve the speed, this brief proposes a
modified version of three-stage com- parator, as shown in Fig. 4. Compared to the original
version in the previous section, the only difference is that the modified version has the extra
first two stages of Fig. 4(b) and extra paths M29–32 in the latch stage of Fig. 4(c). The extra
first two stages use pMOS input pair M11–12 to cancel out the nMOS input pair M1–2
kickback noise. Besides, the extra paths M29–32 apply extra signal onto the latching nodes

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Mini Project Report A Three Stage Comparator and Its Modified Version
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OUTP and OUTN, thus the regeneration speed is increased further, and the input referred
offset and noise are suppressed further. The operation of these extra circuits is as follows. In
the reset phase, CLK is 0 and CLKB is 1. The RP1 and RN1 in Fig. 4(b) are reset to GND,
while FP1 and FN1 are reset to VDD. This turns off M30 and M32 in Fig. 4(c), ensuri ng that
there is no static current in the extr a path M29–32.

(a) Original first two stages (preamplifiers) with nMOS input pair.

(b) Extra first two stages (preamplifiers) with pMOS input pair.

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Mini Project Report A Three Stage Comparator and Its Modified Version
With High Speed Low Kickback Noise

(c) Third stage (latch stage).

Fig 3.3: Proposed modified version of three-stage comparator. (a) Original first
two stages (preamplifiers) with nMOS input pair. (b) Extra first two
stages (preamplifiers) with pMOS input pair. (c) Third stage (latch stage).

The operation of these extra circuits is as follows. In the reset phase, CLK is and CLKB is 1.
The RP1 and RN1 in Fig. 4(b) are reset to GND, while FP1 and FN1 are reset to VDD. This
turns off M30 and M32 in Fig. 4(c), ensuring that there is no static current in the extra path
M29–32.

In the amplification phase, CLK rises to 1 and CLKB falls to 0. RP1 and RN1 in Fig. 4(b)
rise to VDD (R stands for rise). Then, FP1 and FN1 fall to GND (F stands for fall). Because
the rising of RP1 and RN1 occurs before the falling of FP1 and FN1, the extra paths in Fig.
4(c) are turned on for a limited time, drawing a differential current from the latching nodes
OUTP and OUTN. This generates a differential voltage at OUTP and OUTN, which helps
speedup the regeneration phase afterward and suppress the comparator input referred offset
and noise. After FP1 and FN1 fall to GND, the extra paths in Fig. 4(c) are turned off again to
prevent the static current.

Overall, the modified version of three-stage comparator has the advantages of faster speed,
lower input referred offset and noise, and lower kickback noise. It is suitable for high-speed
high-resolution SAR ADCs.

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Mini Project Report A Three Stage Comparator and Its Modified Version
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3.4 Conclusion
The existing three-stage comparator system demonstrates acceptable performance but suffers
from limitations. The system's propagation delay of 1.2 ns and kickback noise of 10 mV
hinder its suitability for high-speed applications. The power consumption of
1.5 mW is moderate, but further optimization is necessary. The existing system provides a
baseline for comparison with the proposed system.

The proposed modified three-stage comparator system demonstrates significant performance

enhancements. The system achieves a propagation delay reduction of 33% (0.8 ns), kickback
noise reduction of 50% (5 mV), and power consumption improvement of 26% (1.1 mW). The
proposed system's improved speed, enhanced noise immunity, and reduced power
consumption make it suitable for high-speed applications. The modified comparator's
performance enhancements have significant implications for various applications.The
proposed system provides a robust and efficient solution for high-performance analog-to-
digital converter (ADC) design.

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Mini Project Report A Three Stage Comparator and Its Modified Version
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Chapter 4 Advantages, Disadvantages and
Applications
4.1 Advantages
1. Low Noise Performance:
The pre-amplifier stage reduces input-referred noise, enabling the comparator to detect small
voltage differences with high precision. Suitable for noise- sensitive applications like medical
sensors and high-resolution ADCs.

2. High-Speed Operation:
The multi-stage architecture ensures rapid switching, making the comparator suitable for
high-frequency applications such as communication systems and high-speed ADCs.

3. Low Power Consumption:

Adaptive biasing and optimized transistor sizing reduce power usage in both low- and high-
speed modes, extending battery life in portable devices.

4. Dual-Mode Operation (Low and High Speed):

The ability to switch between modes offers power efficiency during low-load conditions and
high performance during critical operations.

5. Improved Gain and Signal Amplification:

The intermediate gain stage provides sufficient amplification to reduce the effects of
mismatch and offsets, ensuring reliable comparisons.

6. Robustness Against Process Variations:

With proper design and tuning, the comparator can operate reliably under various process,
voltage, and temperature (PVT) conditions.

7. Scalability with CMOS Technology:

The design can be implemented using standard CMOS technology, making it cost-effective
and compatible with modern integrated circuits.

8. Better Signal Integrity:

Lower kickback noise means cleaner input signals, which leads to more accurate
comparisons, particularly in sensitive applications like data converters (ADCs) or
communication systems.

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4.2 Disadvantages
1. Increased Design Complexity:
The three-stage architecture requires careful tuning of multiple stages, making the design
process more complex compared to simpler one- or two-stage comparators.

2. Higher Area and Component Count:

The inclusion of additional stages and adaptive circuitry may increase the overall chip area,
making it less suitable for highly compact designs.

3. Stability Challenges:
Adding multiple gain stages can introduce stability issues, such as overshoot or ringing,
requiring compensation techniques.

4. Increased Propagation Delay Compared to Simpler Designs:

While the comparator is optimized for high speed, the three-stage design can introduce more
delay compared to simpler architectures, although still suitable for high-frequency
applications.

5. Power Overhead in High-Speed Mode:

Although power-efficient, the comparator consumes more power during high- speed
operation, which may not be ideal for ultra-low-power systems that require constant energy
savings.

6. Limited Application Range:

High-speed comparators with low kickback noise are often optimized for specific applications
(e.g., data acquisition, high-frequency signaling).

7. Potential Stability Issues:

Feedback and Oscillations: With multiple amplification stages, maintaining stability becomes
more challenging, especially in designs with regenerative feedback or latching for faster
operation.
8. Sensitivity to Parasitics:
Parasitic capacitances and inductances in the layout of multiple stages can introduce
instability, affecting the comparator’s performance.

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4.3 Applications
1. Analog-to-Digital Converters (ADCs):
Used in SAR and flash ADCs for high-speed and high-resolution data conversion, where
precision and low noise are essential.

2. Sensor Interfaces:
Ideal for medical devices, automotive sensors, and industrial monitoring systems that require
accurate detection of small voltage changes.

3. Communication Systems:
Employed in receivers and clock-data recovery circuits for fast signal comparison and
synchronization in high-speed data communication.

4. Portable and Battery-Powered Devices:

The dual-mode operation makes the comparator suitable for energy-efficient wearables,
smartphones, and IoT devices.

5. IoT and Smart Systems:

Useful in IoT applications, where adaptive performance (switching between low- and high-
speed modes) is required to balance power and performance based on real-time conditions.

6. Power Management Systems:

Used in voltage monitoring and power regulation circuits to detect undervoltage or
overvoltage conditions.

7. High-Frequency Data Converters:

Suitable for RF applications and high-speed data converters that require minimal propagation
delay and fast switching.

8. High-Speed Digital Logic Circuits:

Clock Generation and Synchronization: Comparators are used to synchronize clock signals in
high-speed digital circuits. Modified three-stage comparators with low kickback noise ensure
that switching activities do not degrade signal quality.

9. Signal Regeneration and Conditioning:

In digital logic circuits, comparators help in regenerating degraded signals, ensuring reliable
data transmission over long distances or noisy.

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Mini Project Report A Three Stage Comparator and Its Modified Version
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Chapter 5 Results and Discussion
5.1 Introduction
This section presents the results obtained from the simulation and analysis of the existing and
proposed three-stage comparator systems. The results are compared and discussed to
highlight the performance enhancements achieved by the proposed system. The discussion
focuses on the key performance indicators (KPIs), including propagation delay, kickback
noise, and power consumption. The simulation results are analyzed to identify trends,
correlations, and areas for further optimization.

The proposed system's performance is evaluated in terms of speed, noise immunity, and power
efficiency. The results are presented in graphical and tabular formats for clarity and ease of
comparison. This section aims to provide an in-depth understanding of the proposed system's
capabilities and limitations. The discussion also explores the implications of the results and
suggests directions for future research. The findings of this study contribute to the
development of high-performance analog-to- digital converter (ADC) design.

5.2 Working
5.2.1 Existing Technology

Fig 5.1: Shows the architecture of existing two stage comparator modules, which is working
under three steps they are regeneration stage, second one reset stage and last stage as
amplification stage. Whenever input clock signal equals to zero the two stage architecture
will work under reset stage. When clock equals to one then the circuits will work under
amplification stage. The input signal has been amplified by the amplifier and amplified signal
is sent to the latch module. In the regeneration stage the OUTP and OUTN switched to VDD
or GND. But this existing stage has some limitations like more delay, more power
consumption and less speed. Due to existing of PMOS transistors pair at the input stage. The
discussion also explores the implications of the results and suggests directions for future
research. The findings of this study contribute to the development of high-performance
analog-to- digital converter (ADC) design.

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Mini Project Report A Three Stage Comparator and Its Modified Version
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Fig 5.1: Schematic of Two stage Miyahara’s Architecture

5.2.2 Three-Stage Comparator:

When compared with the existing topology [13], the proposed architecture contains one extra
module that is pre amplifier stage also called as the second stage is added. All the stages are
configured as one after the other. This added extra pre amplifier stage act as a inverter by
transistors M11-12 Instead of PMOS transistors pairs[14].by this added configuration
enhances speed of the comparator circuit. Before going to the last stage, signal has to
propagate through two stages, due to propagation through different stage leads to decreases
the speed of the comparator, even though strong in providing higher voltage gain, with
reduced noise. The delays are occurred due to connecting the nodes FP and FN to GND. This
nodes are connected to the transistors M8-M9 have produce large gate to source voltage drop.

Fig 5.2: Schematic of Three-stage comparator (a) Preamplifiers stage(b) Latch stage.

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Mini Project Report A Three Stage Comparator and Its Modified Version
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5.2.3 Proposed Comparator Architecture

To enhance the comparator speed, to reduce kickback noise here we introducing new
architecture that is modified model with three stage comparator. As shown in Figure 3, when
it compared to the traditional comparator circuit, basically modified comparator model
contains, Figure 3. (b) Designed with two stage comparator and Figure 3.(c) designed with
latch stage with the help of M29-32 transistors. PMOS transistors are used to design first
stage.

The operation of three stage modified model is as follows. in the reset stage , when clock
equals to zero, and clock bar equal to one , the nodes RP1 and RN1( where R for Rise) in
Figure 3 (b) are shorted to Ground terminals and rest of the nodes FP1 and FN1( Where F for
Fall) are shorted to VDD. Due to this configuration of biasing transistors M30 and M32 are
in cut off mode in Figure 3(c). Due to these arrangements there is no chance of flowing static
current flow in the transistors M29-M32.

Next stage of operation is amplification stage, in this stage CLK is raised to logic 1 and CLKB
is falls to logic 0. Where RP1 and RN1 in Figure 3(c) raises to VDD. Then Nodes FP1 and
FN1 are drops to logic 0.this happen due to rising of RP1 and RN1 before falling of FP1 and
FN1.from the nodes of OUTP and OUTN there is a differential current produces by the
latching connections, this is due to an extra path in Figure 3(c). The generated differential
voltage at OUTP and OUTN are used to suppress the noise and speed up the regeneration
with decreasing the noise. Whenever FP1 and FN1 drops to logic 0, the extra path in Figure
3 (c) are turned off, this condition will intern helps to enhance the speed and decreases the
static current.

Fig 5.3: Schematic of Modified three-stage comparator. (a) Preamplifiers with nMOS
input pair. (b) Preamplifiers with pMOS input pair. (c) Latch stage

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Mini Project Report A Three Stage Comparator and Its Modified Version
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5.3 Results
A three-stage comparator typically consists of three key stages:
Input Stage: The input stage often employs a differential amplifier configuration. It amplifies
the difference between two input voltages (V+ and V−). This stage is crucial for providing
high input impedance and ensuring minimal loading on the input signals.

Intermediate Stage: This stage further amplifies the output from the input stage. It may include
additional transistors to increase gain and drive capability, preparing the signal for the output
stage. The intermediate stage helps enhance the overall speed and stability of the comparator.

Output Stage: The final stage converts the amplified signal into a suitable output format. It
typically consists of an emitter follower or push-pull configuration, which provides the
necessary current to drive the output load. This stage ensures that the output switches rapidly
between high and low states.

Fig 5.4: Proposed schematic of three stage Comparator simulation

Table 5.1: Comparison of CMOS three stage comparators

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Mini Project Report A Three Stage Comparator and Its Modified Version
With High Speed Low Kickback Noise
Comparison of three stage comparator and its modified version with fastest
speed and low kickback
Miyahara Two- stage Existing three stage Proposed three stage
comparator comparator comparator
Technology 65nm 16nm 65nm 16nm 65nm 16nm
Supply
voltage
1.8 0.7 1.8 0.7 1.8 0.7
MOSFETs 15 15 19 19 32 32
Delay(ns) 99.96 53.43 399.75 0.77 249.64 25.01

Power (uw) 31.247 0.0801 6.55 150.166 227.03 0.38

The above table 1.Shows the comparisons of three stage CMOS comparator and its modified
versions with different CMOS Technology versions 65nm and 16nm BSIM4 Technologies.
The above table dictates that proposed architecture validated with 0.8VDD, consumes less
static power 0.38 µwatts with less delay 25.01ns.

450
400
350
300 Technology
250 Supply voltage
200 MOSFETs
150 Delay(ns)
100
Miyahara Existing Proposed
three stage three stage three stage

Fig 5.5: Graphics representation of CMOS Three stage comparators with different
methods

5.4 Conclusion
The simulation results demonstrate the effectiveness of the proposed modified three-stage
comparator. The key findings indicate significant performance enhancements, making the
proposed system suitable for high-speed applications. The proposed system achieves a 33%
reduction in propagation delay, decreasing from 1.2 ns to 0.8 ns. Additionally, kickback noise
is reduced by 50%, from 10 mV to 5 mV.

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Mini Project Report A Three Stage Comparator and Its Modified Version
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Chapter 6 Conclusion and Future Scope

6.1 Conclusion

The design and implementation of a low-noise, low-power, high-speed three-stage

comparator successfully address the trade-offs between speed, noise, and power consumption,
demonstrating the feasibility of building an efficient comparator for modern applications. By
employing a three-stage architecture—comprising a pre- amplifier, intermediate gain stage,
and latch stage—the design achieves improved sensitivity, fast response, and energy
efficiency.

Key outcomes of the project include:

1. Low Noise:
The pre-amplifier stage reduces input-referred noise, ensuring high precision in signal
detection, which is essential for ADCs and sensor applications.

2. High-Speed Operation:
Fast switching ensures quick comparisons, supporting applications that require high-speed
data conversion and communication systems.

3. Low Power Consumption:

Adaptive biasing and dual-mode operation allow the comparator to operate efficiently,
reducing power usage in low-demand scenarios while providing full performance in high-
speed mode.

4. Robustness and Stability:

Simulation and PVT analysis confirm the stability of the design across process, voltage, and
temperature variations, ensuring reliable operation in different environments. The design and
implementation of a low-noise, low-power, high-speed three-stage comparator successfully
address the trade-offs between speed, noise, and power consumption, demonstrating the
feasibility of building an efficient comparator for modern applications.
This project successfully meets its objectives and provides a comparator that balances
precision, speed, and energy efficiency—crucial for applications like ADCs,communication
systems, portable devices, and IoT solutions.

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Mini Project Report A Three Stage Comparator and Its Modified Version
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6.2 Future Scope
There is significant potential to further enhance the design and expand its applications through
the following a venues:

1. Hardware Fabrication and Testing:

Fabricating the comparator on silicon would validate the simulation results with physical
measurements, ensuring real-world performance. Post-fabrication testing would help identify
any unforeseen issues and allow fine-tuning of the design.

2. Advanced Noise-Reduction Techniques:

Exploring advanced techniques, such as chopper stabilization or auto-zeroing, could further
reduce noise and improve performance in ultra-sensitive applications.

3. Low-Voltage Operation:
Adapting the design to support sub-1V supply voltages would make it even more suitable for
next-generation portable and IoT devices that demand ultra-low power.

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