In this project, we will design and build a high-power audio amplifier using the 2SB1560/2SD2390 transistor pair. These NPN (2SD2390) and PNP (2SB1560) transistors are widely used in audio amplification for their ability to provide high output power, making them ideal for this project. We will focus on a specific application: designing an amplifier that can deliver clear, distortion-free audio output at high volume levels suitable for large room speakers or home theater systems.
Introduction to 2SB1560/2SD2390 Transistor Pair
Before diving into the project, let’s take a brief look at the components we'll be working with.● 2SB1560 (PNP Transistor) and 2SD2390 (NPN Transistor) are complementary power transistors, often used in audio applications for their robust power handling and linear performance.
● These transistors are part of a high-power transistor series that provides excellent gain, high efficiency, and low distortion in audio circuits.
● With a maximum collector current of 15A and a collector-emitter voltage of 80V, these transistors can handle the significant power demands of high-end audio amplification.
● The pair is often used in bridge amplifiers, push-pull configurations, and other high-power audio circuits.
Project Overview: High-Power Audio Amplifier
The goal of this project is to build a stereo audio amplifier that can drive high-power speakers, such as 8-ohm or 4-ohm speakers, producing high-quality sound with minimal distortion.This amplifier will have:
● Output Power: Capable of delivering at least 100 watts per channel into an 8-ohm load.
● Low Distortion: Maintaining a high signal-to-noise ratio (SNR) and low total harmonic distortion (THD).
● Thermal Management: Efficient heat dissipation to ensure stable operation under load.
We will use the 2SB1560/2SD2390 transistors as the main power amplification stage and pair them with supporting components like driver transistors, diodes, and heat sinks for optimal performance.
Circuit Design
Power Supply
The amplifier requires a robust power supply that can deliver a stable DC voltage to the amplifier circuits. We will use a dual power supply to provide both positive and negative voltages:● +40V and -40V rails are suitable for driving the amplifier to the desired output power.
● A transformer with a primary voltage of 220V AC and secondary windings of 40V-0-40V will step down the AC mains voltage to the required DC voltage when rectified.
● Rectifiers (diodes) will be used to convert AC to DC, and filter capacitors will smooth the output to ensure a clean supply for the amplifier.
Pre-Amplifier Stage
Before the signal reaches the power transistors, it needs to be amplified to a level suitable for driving the output stage. This is done through a pre-amplifier stage that uses low-power transistors or operational amplifiers. The pre-amplifier increases the low-level audio signal from sources like a smartphone, CD player, or turntable to a level that can drive the power transistors without distortion.The pre-amplifier section typically consists of:
● Input capacitors to block any DC component from the audio source.
● Gain stages that amplify the audio signal using small-signal transistors or op-amps.
● Tone control (optional) to adjust bass, midrange, and treble frequencies.
Driver Stage
The driver stage is critical in delivering the necessary current and voltage to drive the power transistors (2SB1560 and 2SD2390). These power transistors require a higher current to be activated, and without a proper driver stage, they may not function correctly.In this stage, we use transistor pairs to drive the 2SB1560 and 2SD2390. These transistors work as push-pull pairs:
● One transistor will pull the current in one half of the cycle (positive half), while the other pushes the current in the opposite half (negative half).
● This configuration helps in minimizing crossover distortion, which can degrade the sound quality.
Output Stage (2SB1560/2SD2390)
The output stage is where the heavy lifting happens. The 2SB1560 and 2SD2390 transistors act as the final amplification stage, delivering the required power to the speakers.● The 2SB1560 (PNP) transistor is used for the positive half of the waveform, and the 2SD2390 (NPN) transistor is used for the negative half of the waveform.
● These transistors operate in a class AB configuration, which balances efficiency and linearity. The class AB design ensures that the amplifier produces minimal distortion and can run more efficiently than a class A amplifier, which consumes more power.
Feedback and Stability
To achieve a high-quality, stable output, we use a negative feedback loop. The output of the amplifier is fed back into the input stage to ensure that the signal remains linear and free from distortion.● The feedback loop also helps maintain the frequency response of the amplifier and keeps the gain consistent.
● We also use compensation capacitors and biasing circuits to stabilize the amplifier at different temperatures and operating conditions.
Thermal Management
Power transistors like the 2SB1560 and 2SD2390 can generate significant heat during operation. If not managed properly, this heat can cause thermal runaway and damage the components. To prevent this, we will use large heatsinks for the transistors and incorporate thermal pads or thermal grease to ensure effective heat dissipation.● Additionally, a fan can be used to aid in cooling if the amplifier is housed in a compact enclosure.
Assembly
- Prepare the Power Supply:
● Ensure the DC output is clean and stable.
- Build the Pre-Amplifier Stage:
● Integrate the gain stage with an op-amp or small signal transistor.
- Construct the Driver Stage:
● Ensure the driver transistors have proper biasing to prevent distortion.
- Install the Output Stage (2SB1560/2SD2390):
● Connect the collector, base, and emitter terminals to the appropriate points in the driver stage.
- Feedback Loop:
- Final Assembly:
● Ensure the power supply, driver stage, and output stage are connected securely.
Testing and Tuning
After assembling the amplifier, it’s time for testing:- Initial Power On: Check the voltages across key components, ensuring no excessive heat generation.
- Signal Testing: Feed a known audio signal (from a phone or audio generator) and measure the output on an oscilloscope to ensure clean amplification with minimal distortion.
- Fine-Tuning: Adjust the biasing of the transistors and the feedback loop to achieve optimal performance.
- Heat Management: Ensure that the heat sinks are dissipating heat effectively and that the amplifier remains cool during operation.
Conclusion
Building a high-power audio amplifier using the 2SB1560 and 2SD2390 transistors is an incredibly rewarding project that results in a powerful and high-fidelity amplifier capable of driving large speakers with ease. By carefully selecting and assembling the components, you can achieve a customized sound system that outperforms many commercial options while learning a great deal about analog amplification.The process may require patience and attention to detail, but the final product is well worth the effort, providing years of high-quality audio performance.
US 19623 
BR 15761 
GB 12971 
CA 10856 
AU 9468 
IE 4948 
NZ 3327 
IN 1700 
