Electronics Workshop II Project
Author: Aditya Ranjan Padhi Roll Number: 2022122001 Indian Institute of Information Technology Hyderabad
This repository contains the complete design, simulation, analysis, and hardware implementation of a multi-stage audio amplifier designed as part of the Electronics Workshop II course.
The objective of the project is to amplify a low-amplitude microphone signal and drive an 8 Ω loudspeaker using a four-stage amplifier architecture.
The amplifier consists of:
- Current Mirror
- Differential Pre-Amplifier
- Active Load Stage
- Common Source Gain Stage
- Low-Pass Filter
- Class-AB Power Amplifier
| Parameter | Value |
|---|---|
| Supply Voltage | 12 V |
| Microphone Input | 20 mVpp |
| Required Gain | 500 |
| Output Voltage | 10 Vpp |
| Speaker Load | 8 Ω |
| Output Power | Approximately 1 W |
Microphone
│
▼
Differential Amplifier
│
▼
Active Load Stage
│
▼
Common Source Amplifier
│
▼
Low-Pass Filter
│
▼
Class-AB Power Amplifier
│
▼
8 Ω Speaker
A MOSFET current mirror using 2N7000 devices is used to generate a stable current source.
Features:
- Approximately 1 mA bias current
- Improves differential amplifier operation
- Enhances gain and linearity
The differential amplifier provides the initial voltage gain while rejecting common-mode signals.
Features:
- Differential gain ≈ 200
- Common-mode rejection
- 1 mA tail current
- 2N7000 MOSFET pair
PMOS active loads replace drain resistors to:
- Increase gain
- Maintain saturation
- Provide single-ended output
Devices used:
- IRF9540N PMOS
The second gain stage increases the output swing to approximately 10 Vpp.
Features:
- Gain ≈ 35
- Source degeneration
- Bypass capacitor for increased AC gain
A passive RC filter removes high-frequency noise.
Specifications:
- Cutoff frequency: 8 kHz
- Capacitor: 1 nF
- Resistor: 20 kΩ
The output stage drives an 8 Ω speaker.
Features:
- Push-pull configuration
- High efficiency
- Reduced crossover distortion
Devices:
- TIP31C
- TIP32C
- 1N4151 diodes
The amplifier achieves:
- Differential gain ≈ 200
- Overall gain ≈ 500
- Output swing ≈ 10 Vpp
- Low-frequency audio amplification
- Successful speaker drive
Oscilloscope and simulation results are included throughout the report.
The amplifier was physically implemented and tested.
Practical observations:
- Device parameters differed from theoretical values.
- Bias voltages required adjustment.
- Component values were tuned experimentally.
- Hardware measurements closely matched simulations.
- Proteus
- Desmos
- Oscilloscope measurements
- Manual analytical calculations
- 2N7000
- IRF9540N
- TIP31C
- TIP32C
- 1N4151
- Resistors
- Ceramic capacitors
- Electrolytic capacitors
- THD measurement
- CMRR characterization
- Stability analysis
- Active filter implementation
- PCB design
- SPICE optimization
The complete project report is available in:
Report.pdf
The author would like to thank:
- Arti Yardi Ma'am
- Anshu Sarje Ma'am
- Course Teaching Assistants
for their guidance and support throughout the project.
Aditya Ranjan Padhi Electronics and Communication Engineering Indian Institute of Information Technology Hyderabad
This project is provided for academic and educational purposes.
Copyright © Aditya Ranjan Padhi. All rights reserved.