A high-quality audio amplifier is essential for delivering clear and powerful sound. This 80W amplifier circuit is built using MJL4281A / MJL4302A power transistors, known for their efficiency and stability. It is an easy-to-build amplifier with excellent performance, making it ideal for home audio systems, bi-amped setups, or bridge-tied load (BTL) applications.
🔹 Key Features of the 80W Amplifier Circuit
🔹 Power Output: 60W to 80W
🔹 Transistors Used: MJL4281A / MJL4302A (Power) & MJE15034 / MJE15035 (Driver)
🔹 High Efficiency & Low Distortion
🔹 Stable & Reliable Circuit Design
🔹 Ideal for Home Audio & DIY Projects
This amplifier is designed with simplicity and efficiency in mind, ensuring excellent sound clarity while being easy to assemble.
🔹 How the Circuit Works
The amplifier circuit follows a three-stage design:
- Input Stage:
- The input audio signal is pre-amplified using a differential pair, ensuring low distortion and high gain.
- Driver Stage:
- The MJE15034 / MJE15035 transistors act as driver transistors, providing enough power to control the output stage.
- Output Stage:
- The MJL4281A (NPN) and MJL4302A (PNP) transistors handle the power amplification, delivering a clear and powerful 80W output to the speaker.
The circuit includes current protection to prevent damage to components and maintains thermal stability to ensure long-lasting performance.
🔹 Required Components
To build this 80W power amplifier, you will need:
| Component | Value | Function |
|---|---|---|
| Q1, Q2 | MJE15034 / MJE15035 | Driver Transistors |
| Q3, Q4 | MJL4281A / MJL4302A | Power Output Transistors |
| R1, R2 | 1KΩ (1/4W) | Bias & Feedback Resistors |
| R3, R4 | 100Ω (1/4W) | Signal Filtering |
| R5 | 0.22Ω (5W) | Current Limiting Resistor |
| C1 | 10µF (25V) | Input Coupling Capacitor |
| C2 | 100µF (63V) | Power Supply Stabilization |
| D1, D2 | 1N4148 | Voltage Protection |
| Power Supply | ±40V DC | Provides necessary voltage |
🔹 Circuit Diagram Explanation
🔹 Input Signal Processing:
- The audio input passes through a low-pass filter, reducing unwanted noise.
- The differential amplifier processes the signal and adjusts gain.
🔹 Amplification Stages:
- The driver transistors (MJE15034 / MJE15035) boost the signal.
- The MJL4281A / MJL4302A transistors provide final power amplification.
🔹 Output Stage:
- The amplified signal is fed into the speaker for a powerful 80W output.
This efficient design ensures low distortion, high power output, and reliable operation.
🔹 Why Choose This 80W Amplifier Circuit?
✅ High Audio Fidelity – Produces clean, distortion-free sound.
✅ Stable & Reliable – Uses high-quality power transistors.
✅ Easy to Build – Uses commonly available electronic components.
✅ Perfect for DIY Enthusiasts – Ideal for home audio projects and professional setups.
This DIY amplifier project is perfect for audiophiles looking for a powerful yet simple design.
🔹 Conclusion
The 80W power amplifier circuit using MJL4281A and MJL4302A transistors is an efficient, high-performance solution for audio enthusiasts. With its stable output, low distortion, and excellent power handling, this amplifier is ideal for home and professional use.
Would you like to try building this amplifier? Let us know your thoughts in the comments!
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