Course: ELE402 – Electronics Lab
Instructor: Mr. Chadi T. Chamoun
University: Lebanese American University
Date: 11 May 2025
- Ali Awada
- Malak Darwich
- Dana Hachem
- Mahdi Zein Al Dine
This project involved the design, simulation, and hardware implementation of a complete Amplitude Modulation (AM) Receiver, structured into three functional stages:
- Passive Demodulator – Extracts the baseband audio signal using envelope detection with a germanium diode and an RC low-pass filter.
- Baseband Amplifier – A non-inverting op-amp amplifier with adjustable gain to boost the demodulated signal.
- Class A Output Stage – A high-current BJT amplifier designed to drive an 8Ω speaker with sufficient power.
Each stage was simulated using LTspice, then physically implemented and tested on a breadboard and later soldered onto a perforated board.
| Component | Model/Value | Quantity |
|---|---|---|
| Resistors | 1kΩ, 510Ω, 130Ω, etc. | Multiple |
| Capacitors | 1μF, 22μF, 1.8nF | Multiple |
| Diode | OA71 (germanium) | 1 |
| Transistors | BC337 | 12 |
| Op-Amp | TL084 | 1 |
| Speaker | 8Ω | 1 |
| Breadboard, wires, IC sockets, etc. | — | — |
Full bill of materials with prices is included in the report.
Simulations were carried out using LTspice for:
- Signal demodulation
- Frequency response & gain analysis
- Output waveform behavior at various frequencies
Hardware tests included:
- Oscilloscope visualization of input/output signals
- Audio playback via speaker for various tone frequencies
- Gain calibration using voltage divider and potentiometer
- Thermal analysis and heat dissipation management
- Envelope detection using a germanium diode (low forward voltage drop)
- Adjustable gain via potentiometer for volume control
- Parallel BJTs in output stage to handle high current
- Smoothing filters and voltage dividers for optimal stage integration
- Oscilloscope-verified signal integrity across all stages
- High diode forward voltage caused signal clipping → solved by switching to OA71
- Excessive gain in baseband amp → solved with input voltage divider
- Overheating resistors in Class A stage → solved with resistor power rating adjustments
- Transistor overheating → solved by using multiple BJTs in parallel
- Soldering errors → resolved with continuity testing and careful debugging
- Low speaker volume at times
- Limited frequency response above 10kHz
- Significant power consumption in output stage
- Heat buildup during extended operation
This project successfully demonstrated the design and implementation of a working analog AM receiver. Each stage was theoretically analyzed, simulated, constructed, and tested. The final system was able to clearly demodulate and play AM-modulated audio signals. The project provided deep hands-on experience in analog circuit design, troubleshooting, and communication systems.
AM_Demodulator.asc– LTspice simulationBaseband_Amplifier.ascClassA_Output_Stage.ascAM_Receiver.ascFinalReport.pdf– Full technical report (if exported as PDF)README.md
- GeeksForGeeks: Amplitude Modulation Explained
- Vedantu: Why AM is used for long-distance communication
- ELE402 Course Materials and SPICE models
🔧 Built with analog components, teamwork, and lots of oscilloscope debugging!