End Semester Project Report on

DC REGULATED POWER SUPPLY

Submitted for the partial fulfillment of the subject

ANALOG CIRCUITS WORKSHOP

(EET1707)

Group Members
Shristy Kumari (24E111C10)
Ashish Kumar (24E111C41)
Subham Kumar Mishra (24E113B02)

B. Tech. 1st Semester (Section– 24E1U1)

DEPT. OF ELECTRONICS & COMMUNICATION ENGINEERING

Institute of Technical Education and Research
SIKSHA ‘O’ ANUSANDHAN
DEEMED TO BE UNIVERSITY
Bhubaneswar, Odisha, India.
(2025)

i
 Abstract
A DC Regulated Power Supply (DC PSU) is a crucial
component in many electronic systems, providing a stable and
controlled output voltage for powering devices and circuits.
This project focuses on the design and construction of a basic
DC regulated power supply that ensures a consistent DC output
despite fluctuations in input voltage or varying load conditions.
The power supply utilizes a step-down transformer, a bridge
rectifier, a filter capacitor, and a voltage regulator (such as the
LM7812) to convert high-voltage AC to a smooth and stable DC
voltage. The transformer reduces the AC mains voltage, while
the rectifier converts AC into a pulsating DC, which is then
filtered by the capacitor to reduce ripple. The voltage regulator
maintains the output voltage at a fixed level, ensuring
reliability and precision. The project aims to demonstrate the
working principles of AC to DC conversion, voltage regulation,
and the importance of filtering in providing a steady output for
powering electronic devices. Through the assembly and testing
of the power supply, this project offers insights into basic
electronics and power management techniques commonly used
in laboratories, test equipment, and embedded systems.

i
 Contents

Abstract................................................................................................i
Contents...............................................................................................ii
Chapter 01: Introduction.............................................................................1
1.1. Introduction................................................................................................. 1
1.2. Background................................................................................................. 1
1.3. Project Objectives......................................................................................... 1
1.4. Scope......................................................................................................... 1
1.5. Project Management...................................................................................... 1
1.6. Overview and Benefits.................................................................................... 2
Chapter 02: Theoretical Aspects.....................................................................3
2.1. Background Theory and Modeling.....................................................................3
2.2. Project Layout.............................................................................................. 3
2.2.1. Brief Description...................................................................................... 3
2.2.2. Block Diagram of the Proposed System..........................................................3
2.2.3. Working of the system...............................................................................3
2.2.4. Flow Chart / Pseudocode............................................................................3
Chapter 03: Hardware and Software Requirements...............................................4
3.1. Operational Amplifier..................................................................................... 4
3.1.1. Differential Amplifier................................................................................5
3.1.2. Equivalent Circuit of an Ideal Operational Amplifier.........................................6
3.1.3. Op-amp Parameter and Idealized Characteristic................................................6
3.2. Open-loop Frequency Response Curve................................................................7
3.3. An Operational Amplifier Bandwidth....................................................................................8
3.4. Ideal characters of an Op-Amp:...............................................................9
3.5. OPAMP Pin Configuration:.......................................................................10
Chapter 04: Project Development & Testing Aspects.............................................11
4.1. Test Results............................................................................................... 11
4.2. Interpretation of Results................................................................................ 11
Chapter 05: Conclusion & Future Scope..........................................................12
5.1. Conclusion................................................................................................ 12
5.2. Limitations................................................................................................ 12
5.3. Further Enhancement and Future Scope.............................................................12
References...........................................................................................13

ii
Appendix 01.........................................................................................14
A01.1. Data Sheet I................................................................................................ 14
A01.2. Data Sheet II............................................................................................... 14

iii
 Chapter 01: Introduction

1.1. Introduction

A DC Regulated Power Supply is a fundamental electronic device used to

provide a stable and controlled DC voltage to power various electronic circuits
and systems. Unlike unregulated power supplies, which can experience voltage
fluctuations due to changes in load or input voltage, a regulated power supply
ensures that the output voltage remains constant under different operating
conditions. This stability is crucial in applications where precise voltage is
required, such as in testing, powering sensitive equipment, and embedded
systems development.

The basic functioning of a DC regulated power supply involves converting

high-voltage alternating current (AC) from the power grid into a low-voltage
direct current (DC) that can be safely used by electronic circuits. This
conversion is typically achieved in several stages: step-down transformer,
rectification, filtering, and voltage regulation. The transformer reduces the
AC voltage to a lower value, the rectifier converts the AC to pulsating DC, the
filter capacitor smoothens the output, and the voltage regulator ensures that the
output remains stable despite variations in the input or load.

The design and construction of a DC regulated power supply are not only
essential for powering electronic devices but also serve as an excellent
introduction to key electronic concepts, such as AC to DC conversion, filtering,
and voltage regulation. The project presented here demonstrates the practical
application of these concepts by constructing a simple, reliable, and cost-
effective DC regulated power supply capable of providing a stable output
voltage, which is vital for various laboratory and real-world applications.

Through this project, we will explore the components involved, the principles of
operation, and the challenges faced in creating a functional and efficient DC
power supply. The resulting power supply can be used for powering low-
voltage devices and testing circuits in an educational or professional setting.
1.2. Background

The need for reliable and stable DC power emerged as electronic devices
became more complex, particularly with the advent of radio and
telecommunications technology in the early 20th century. Before regulated
power supplies were common, most devices were powered by unregulated
sources, which provided a fluctuating DC voltage that could vary significantly
based on load changes and input voltage.

The development of regulated power supplies was driven by the requirement for
more precise and stable voltage levels. Early power supplies relied on simpler
linear designs, where the regulation was achieved through the use of voltage
regulators such as Zener diodes or series pass transistors.

1.3. Project Objectives

 Design a stable, regulated output voltage that is unaffected by input or

load variations.
 Ensure input voltage compatibility for global use and diverse power
sources.
 Optimize energy efficiency to minimize waste heat and improve
performance.
 Incorporate safety features to protect against overvoltage, overcurrent,
and thermal damage.
 Minimize output ripple and noise for sensitive equipment.
 Develop a compact, cost-effective solution without sacrificing quality or
performance.
 Allow for adjustable output for applications requiring varied power
levels.
 Ensure robust performance under different load conditions.
 Comply with relevant safety standards for reliable operation across
different sectors.
 Design for easy integration into systems for broad applicability.

1.4. Scope
1.5. Project Management
According to the PMBOK Guide (Project Management Body of Knowledge), a project management
life cycle consists of 5 distinct phases including initiation, planning, execution, review, and closure
that combine to turn a project idea into a working product.

Figure 1. Model of phases in project management.

The project initiation phase is the first stage of turning an abstract idea into a meaningful goal. In this
stage, we need to develop a business case and define the project on a broad level.
The project planning stage requires complete diligence as it lays out the project’s roadmap.
The project execution stage is where the project team does the actual work. The job of a project
manager is to establish efficient workflows and carefully monitor the progress of the team.
In the project management process, the third and fourth phases are not sequential in nature. The
project monitoring and controlling phase run simultaneously with project execution.
The project closure stage indicates the end of the project after the final delivery.

1.6. Overview and Benefits

 Chapter 02: Theoretical Aspects

1.7. Background Theory and Modeling

Background Theory

An active wide band-pass filter is designed to allow frequencies within a specific range (bandwidth)
to pass while attenuating frequencies outside this range. The key components of the filter's design and
operation rely on both passive and active elements:

Passive Components (Resistors, Capacitors): Determine the frequency range and provide the basic
filtering functionality.

Active Components (Operational Amplifiers): Provide signal amplification, improve performance,

and eliminate the need for inductors.

Key Parameters

1. Center Frequency ():

The midpoint of the passband, given by:

f_c = \sqrt{f_L \cdot f_H}

2. Bandwidth ():
The range of frequencies allowed to pass:

BW = f_H - f_L

3. Quality Factor ():

Indicates the sharpness of the filter's frequency response:

Q = \frac{f_c}{BW}
4. Gain ():
Amplification provided by the active components, expressed as:

A_v = \frac{V_{out}}{V_{in}}

Modeling of Active Wide Band-Pass Filter

The circuit can be modeled using standard filter configurations, such as the Sallen-Key topology or
multiple feedback (MFB) topology, depending on the desired performance.

1. Transfer Function

The transfer function of an active wide band-pass filter describes its frequency response:

H(s) = \frac{A \cdot s}{s^2 + \frac{s}{Q} + \omega_0^2}

: Angular frequency at the center frequency.

: Quality factor.

2. Circuit Representation

A typical circuit includes:

Two RC networks for setting the lower () and upper () cutoff frequencies.

An operational amplifier for gain and feedback control.

Design Steps

1. Choose Desired Specifications: Define , , , , and .

2. Select Component Values: Use standard equations to calculate resistor and capacitor values.

3. Determine Gain: Design the feedback network of the operational amplifier to achieve the desired
gain.

4. Simulate and Validate: Use circuit simulation tools to verify the frequency response and adjust
component values as needed.

Applications in Real-World Scenarios

The theory and modeling of active wide band-pass filters enable their use in:

Signal filtering in communication systems.

Audio equalization and noise reduction.

Biomedical instrumentation for filtering physiological signals.

By integrating theoretical understanding with practical design principles, active wide band-pass filters
deliver precise and adaptable solutions for a wide range of applications.

1.8. Project Layout

Figure 2. Layout of project module

1.8.1. Brief Description

1.8.2. Block Diagram of the Proposed System

1.8.3. Working of the system

An active wide band pass filter allows a specific range of frequencies to pass through while
attenuating frequencies outside this range. Unlike passive filters, it uses active components (e.g.,
operational amplifiers) to amplify the signal and improve performance. Here's a breakdown of how
the system works:

1. Components of the System

Resistors (R): Define the cut-off frequencies and control the bandwidth.

Capacitors (C): Work with resistors to determine the frequency response.

Operational Amplifier (Op-Amp): Provides amplification and prevents signal attenuation.

Power Supply: Provides the necessary power for the op-amp to function.

2. Design Principle

The filter is designed by combining:

1. High-Pass Filter (HPF): Allows frequencies above a lower cut-off frequency ().

2. Low-Pass Filter (LPF): Allows frequencies below an upper cut-off frequency ().
The overall system is a cascade of these two filters, creating a passband between and .

3. Working Steps

1. Input Signal:

A signal containing a wide range of frequencies is fed into the system.

2. High-Pass Section:

The input signal first passes through the high-pass filter, which attenuates frequencies below .

Only frequencies higher than proceed to the next stage.

3. Low-Pass Section:

The output of the high-pass filter is sent to the low-pass filter, which attenuates frequencies above .
The remaining signal contains frequencies in the range between and .
4. Amplification:

The operational amplifier amplifies the signal, compensating for any losses and enhancing signal
strength.

5. Output Signal:

The final output is a filtered signal containing only frequencies within the passband to .

4. Key Equations

Lower Cut-Off Frequency ():

f_L = \frac{1}{2 \pi R_1 C_1}
f_H = \frac{1}{2 \pi R_2 C_2}
BW = f_H - f_L
A_v = 1 + \frac{R_f}{R_i}
Advantages of the System

Sharp Frequency Selection: Precisely defines the passband.

Amplification: Provides gain to the output signal.

Adjustability: Components like resistors and capacitors can be tuned to change the filter
characteristics.

Low Signal Distortion: Maintains signal integrity within the passband.

1.8.4. Flow Chart / Pseudocode

 Chapter 03: Hardware and Software
Requirements

1.9. Operational Amplifier

Operational Amplifiers, or Op-amps as they are more commonly called, are one of
the basic building blocks of Analogue Electronic Circuits.

Operational amplifiers are linear devices that have all the properties required for
nearly ideal DC amplification and are therefore used extensively in signal
conditioning, filtering or to perform mathematical operations such as add, subtract,
integration and differentiation.

An Operational Amplifier, or op-amp for short, is fundamentally a voltage

amplifying device designed to be used with external feedback components such as
resistors and capacitors between its output and input terminals. These feedback
components determine the resulting function or “operation” of the amplifier and by
virtue of the different feedback configurations whether resistive, capacitive or both,
the amplifier can perform a variety of different operations, giving rise to its name of
“Operational Amplifier”.

An Operational Amplifier is a three-terminal device that consists of two high-

impedance inputs. One of the inputs is called the Inverting Input, marked with a
negative or “minus” sign, ( – ). The other input is called the Non-inverting Input,
marked with a positive or “plus” sign ( + ).

A third terminal represents the operational amplifiers output port which can both sink
and source either a voltage or a current. In a linear operational amplifier, the output
signal is the amplification factor, known as the amplifier gain ( A ) multiplied by the
value of the input signal, and depending on the nature of these input and output
signals, there can be four different classifications of operational amplifier gain.

 Voltage – Voltage “in” and Voltage “out”

  Current – Current “in” and Current “out”
 Transconductance – Voltage “in” and Current “out”
 Trans-resistance – Current “in” and Voltage “out”

The output voltage signal from an Operational Amplifier is the difference between the
signals being applied to its two individual inputs. In other words, an op-amps output
signal is the difference between the two input signals as the input stage of an
Operational Amplifier is in fact a differential amplifier as shown below.

1.9.1. Differential Amplifier

The circuit below shows a generalized form of a differential amplifier with two inputs
marked V1 and V2. The two identical transistors TR1 and TR2 are both biased at the
same operating point with their emitters connected together and returned to the
common rail, - Vee by way of resistor Re.

The circuit operates from a dual supply +Vcc and -Vee which ensures a constant
supply. The voltage that appears at the output, Vout of the amplifier, is the
difference between the two input signals as the two base inputs are in anti-phase
with each other.

So as the forward bias of transistor, TR1 is increased, the forward bias of transistor
TR2 is reduced and vice versa. Then if the two transistors are perfectly matched, the
current flowing through the common emitter resistor, Re will remain constant.

Like the input signal, the output signal is also balanced and since the
collector voltages either swing in opposite directions (anti-phase) or in the
same direction (in-phase) the output voltage signal, taken from between the
two collectors is, assuming a perfectly balanced circuit the zero difference
between the two collector voltages.
 This is known as the Common Mode of Operation with the common mode gain of
the amplifier being the output gain when the input is zero.

Operational Amplifiers also have one output (although there are ones with an
additional differential output) of low impedance that is referenced to a common
ground terminal and it should ignore any common mode signals that is, if an identical
signal is applied to both the inverting and non-inverting inputs there should no
change to the output.

However, in real amplifiers, there is always some variation, and the ratio of the
change to the output voltage with regards to the change in the common mode input
voltage is called the Common Mode Rejection Ratio or CMRR for short.

Operational Amplifiers on their own have a very high open loop DC gain and by
applying some form of Negative Feedback we can produce an operational amplifier
circuit that has a very precise gain characteristic that is dependent only on the
feedback used. Note that the term “open loop” means that there are no feedback
components used around the amplifier so the feedback path or loop is open.

An operational amplifier only responds to the difference between the voltages on its
two input terminals, known commonly as the “Differential Input Voltage” and not to
their common potential. Then if the same voltage potential is applied to both terminals
the resultant output will be zero. An Operational Amplifiers gain is commonly known
as the Open Loop Differential Gain and is given the symbol (Ao).

1.9.2. Equivalent Circuit of an Ideal Operational Amplifier

1.9.3. Op-amp Parameter and Idealized Characteristic

Open Loop Gain, (Avo)

 Infinite – The main function of an operational amplifier is to amplify the input
signal, and the more open loop gain it has the better. Open-loop gain is the gain of the
op-amp without positive or negative feedback and for such an amplifier the gain will
be infinite but typical real values range from about 20,000 to 200,000.

Input impedance, (ZIN)

Infinite – Input impedance is the ratio of input voltage to input current and is
assumed to be infinite to prevent any current flowing from the source supply into the
amplifiers input circuitry (IIN = 0). Real op-amps have input leakage currents from a
few pico-amps to a few milli-amps.

Output impedance, (ZOUT)

Zero – The output impedance of the ideal operational amplifier is assumed to be
zero acting as a perfect internal voltage source with no internal resistance so that it
can supply as much current as necessary to the load. This internal resistance is
effectively in series with the load thereby reducing the output voltage available to the
load. Real op-amps have output impedances in the 100-20kΩ range.

Bandwidth, (BW)
Infinite – An ideal operational amplifier has an infinite frequency response and
can amplify any frequency signal from DC to the highest AC frequencies, so it is
therefore assumed to have an infinite bandwidth. With real op-amps, the bandwidth is
limited by the Gain-Bandwidth product (GB), which is equal to the frequency where
the amplifiers gain becomes unity.

Offset Voltage, (VIO)

Zero – The amplifiers output will be zero when the voltage difference between the
inverting and the non-inverting inputs is zero, the same or when both inputs are
grounded. Real op-amps have some output offset voltage.

From these “idealized” characteristics above, we can see that the input resistance is
infinite, so no current flows into either input terminal (the “current rule”) and that
the differential input offset voltage is zero (the “voltage rule”). It is important to
remember these two properties as they will help us understand the workings of the
Operational Amplifier with regard to the analysis and design of op-amp circuits.

However, real Operational Amplifiers such as the commonly available uA741, for
example, do not have infinite gain or bandwidth but have a typical “Open Loop Gain”
which is defined as the amplifiers output amplification without any external feedback
signals connected to it and for a typical operational amplifier is about 100dB at DC
(zero Hz). This output gain decreases linearly with frequency down to “Unity Gain”
or 1, at about 1MHz and this is shown in the following open-loop gain response
curve.

1.10. Open-loop Frequency Response Curve

From this frequency response curve, we can see that the product of the gain against
frequency is constant at any point along the curve. Also, the unity gain (0dB)
frequency also determines the gain of the amplifier at any point along the curve. This
constant is generally known as the Gain Bandwidth Product or GBP. Therefore:
 GBP = Gain x Bandwidth = A x BW

For example, from the graph above the gain of the amplifier at 100kHz is given as
20dB or 10, then the gain bandwidth product is calculated as:

GBP = A x BW = 10 x 100,000Hz = 1,000,000.

Similarly, the operational amplifiers gain at 1kHz = 60dB or 1000, therefore the
GBP is given as:

GBP = A x BW = 1,000 x 1,000Hz = 1,000,000.

The Voltage Gain (AV) of the operational amplifier can be found using the following
formula:

and in Decibels or (dB) is given as:

1.11. An Operational Amplifiers Bandwidth

The operational amplifier bandwidth is the frequency range over which the voltage
gain of the amplifier is above 70.7% or -3dB (where 0dB is the maximum) of its
maximum output value as shown below.
 Here we have used the 40dB line as an example. The -3dB or 70.7% of Vmax down
point from the frequency response curve is given as 37dB. Taking a line across until it
intersects with the main GBP curve gives us a frequency point just above the 10kHz
line at about 12 to 15kHz. We can now calculate this more accurately as we already
know the GBP of the amplifier, in this particular case 1MHz.

1.12. Ideal characters of an Op-Amp:

Open Loop gain
Open loop gain is the gain of the Op Amp without positive or negative feedback. An ideal
OP Amp should have an infinite open loop gain but typically it ranges between 20,000
and 2, 00000.

Input impedance
It is the ratio of the input voltage to the input current. It should be infinite without any
leakage of current from the supply to the inputs. But there will be a few Pico ampere
current leakages in most Op-Amps.

Output impedance
The ideal Op Amp should have zero output impedance without any internal resistance. So
that it can supply full current to the load connected to the output.
Band-width
The ideal Op Amp should have an infinite frequency response so that it can amplify any
frequency from DC signals to the highest AC frequencies. But most Op Amps have
limited bandwidth.

Offset
The output of the Op Amp should be zero when the voltage difference between the inputs
is zero. But in most Op Amps, the output will not be zero when off but there will be a
 minute voltage from it.

1.13. OPAMP Pin Configuration:

In a typical Op-Amp there will be 8 pins.

These are

Pin1 – Offset Null

Pin2 – Inverting input INV
Pin3 – Non-inverting input Non-INV
Pin4 – Ground- Negative supply
Pin5 – Offset Null
Pin6 – Output
Pin7 – Positive supply
Pin8 – Strobe
 Chapter 04: Project Development &
Testing Aspects
1.14. Test Results

1.15. Interpretation of Results

 Chapter 05: Conclusion & Future Scope

1.16. Conclusion
The design and implementation of an active wide band-pass filter play a critical role in
modern signal processing applications. By combining passive and active components, this filter offers
significant advantages, including signal amplification, enhanced selectivity, and tunability, which are
not achievable with traditional passive filters.

Active wide band-pass filters are particularly suited for applications requiring precise control over a
broad frequency range, such as communication systems, audio processing, and biomedical
instrumentation. Their ability to operate with low noise, compact design, and high energy efficiency
makes them ideal for both portable and large-scale systems.

This study demonstrates that the active wide band-pass filter provides a flexible and reliable solution
for filtering tasks, supporting both theoretical models and practical implementations. Future
advancements in materials and circuit design can further enhance the performance of these filters,
expanding their applications in emerging technologies like IoT, wearable devices, and high-frequency
communication systems.

In conclusion, the active wide band-pass filter remains a cornerstone in signal processing, offering a
perfect balance of performance, versatility, and scalability for various modern electronic applications.

1.17. Limitations
While active wide band-pass filters offer numerous advantages, they also have certain
limitations that must be considered during design and application:

1. Frequency Range Limitations

Active filters are typically limited to low and medium frequency ranges due to the finite gain-
bandwidth product of operational amplifiers. At very high frequencies, the performance degrades
significantly.

2. Power Supply Dependency

Active components, such as operational amplifiers, require a stable power supply. This can add
complexity and cost to the system, especially in portable or battery-operated devices.
3. Thermal Stability

The performance of active filters can be affected by temperature variations, as the characteristics of
active components (e.g., op-amps) may drift with changes in temperature.

4. Limited Signal Handling Capability

Active filters may not handle high-power signals efficiently due to the voltage and current limitations
of the active components. This restricts their use in high-power applications.

5. Component Non-Idealities

Non-ideal behavior of operational amplifiers, such as input bias currents, offset voltages, and finite
slew rates, can degrade the performance of the filter.

Resistors and capacitors have tolerances that can lead to variations in the filter's frequency response.

6. Noise and Distortion

The active components introduce noise and distortion, which may affect the quality of the filtered
signal, especially in sensitive applications like audio or biomedical devices.

7. Complexity in High-Order Filters

Designing high-order filters (with sharper roll-off and higher selectivity) increases circuit complexity
and may require multiple operational amplifiers, making the design less efficient.

8. Size and Power Consumption for Complex Designs

Although compact compared to passive filters with inductors, active filters with multiple stages or
high gain may consume more power and occupy more space in integrated systems.

1.18. Further Enhancement and Future Scope

Future Enhancements for Active Wide Band Pass Filters

1. Integration with Emerging Technologies:

AI and Machine Learning: Use adaptive algorithms to optimize filter parameters in real-time for
dynamic environments.
IoT Compatibility: Develop filters integrated with IoT devices for real-time signal processing in
remote or smart systems.

2. Miniaturization:

Further reduce the size of active wide band pass filters using advanced semiconductor materials and
MEMS (Micro-Electro-Mechanical Systems) technology for portable and wearable devices.

3. Improved Efficiency:

Implement energy-efficient designs to minimize power consumption, particularly for battery-powered

applications.

Utilize advanced operational amplifiers with lower noise and distortion.

4. Wider Frequency Ranges:

Extend operational bandwidths to accommodate high-frequency applications, such as 5G

communication and ultra-wideband (UWB) systems.

5. Programmable Filters:

Design digitally tunable filters to allow real-time adjustment of bandwidth and center frequencies for
applications in software-defined radios (SDR).

6. Integration with Photonic Systems:

Incorporate optical components for higher data rates and reduced electromagnetic interference in
communication systems.

Future Scope for Active Wide Band Pass Filters

1. 5G and Beyond:

Support advanced communication standards by providing precise filtering for high-speed, low-latency
applications.

2. Biomedical Applications:

Use in medical devices for precise signal processing, such as ECG and EEG signal extraction and
noise reduction.

3. Automotive Industry:

Apply in autonomous vehicles for filtering radar and LiDAR signals, enabling accurate object
detection.
4. Space and Defense:

Use in satellite communication and military applications for signal integrity in harsh environments.

5. Audio and Multimedia:

Enhance audio processing in modern devices like hearing aids, smart speakers, and high-fidelity
sound systems.

6. Quantum Computing:

Play a role in signal conditioning and noise reduction in quantum systems, enabling more accurate
data processing.
References
 Appendix 01
A01.1. Data Sheet I

A01.2. Data Sheet II