Have you ever wondered how those
professional power amplifiers work that can deliver 100W of
crystal-clear audio? Most use complementary transistors in
the output stage, usually an NPN/PNP pair working in
perfect harmony.
But today we're going to explore a
very interesting and less common configuration: a robust
amplifier using two NPN 2SC5200 transistors at the output.
Why do this? Simple:
to test, learn and challenge conventions!
This project is perfect for:
Students of electronics who want to understand
high-fidelity amplifiers
Designers looking for a reliable and well-documented
topology
Hobbyists who enjoy building their own amplifiers
Technicians interested in experimenting with different
transistor configurations
🔍 Why Two NPN Transistors at the Output?
The complementary amplifier topology is the gold standard
in professional audio, but this project
intentionally breaks that rule, as it recalls the times
when PNP power transistors were quite expensive and less accessible.
Using two transistors of the same polarity (NPN), you can achieve:
✅ Better understanding of Class AB and Class B
amplifiers
✅ Experimental flexibility to test different topologies
✅ Satisfactory sound quality for home and DIY
applications
✅ Solid foundation for more complex projects
The 2SC5200 transistors were selected for their
excellent frequency response and
stable gain,fundamental
characteristics for high-fidelity amplification.
🔌 Circuit Schematic Diagram
Figure 2 below presents the complete schematic diagram of
the amplifier. This circuit has been optimized to offer:
📊 100W RMS output with typical load impedance (4-8Ω)
🔊 Extended frequency response without audible distortion
⚡ Overload protection and excessive heating
🛡️ Thermal stability with balanced components
Fig. 2 – Complete Schematic Diagram: 100W RMS Power Amplifier with 2 NPN
2SC5200 Transistors at Output
Note the modular structure of the circuit: input stage
(coupling), pre-amplification, driver stage and, finally, the power stage
with the two 2SC5200. Each section has been carefully
designed to minimize distortion and maximize efficiency.
⚡ Symmetrical Power Supply
The amplifier's power supply is symmetrical, meaning it
uses positive and negative voltages in
relation to ground (center point). This is the
ideal configuration for quality audio amplifiers.
📌 Recommended Specifications
Parameter
Recommended Value
Transformer Voltage
45V - 0 - 45V (center-tape)
Transformer Current
5A (minimum: 3A)
Operating Range
±35V to ±55V (with power variation)
Power Supply Type
Linear or SMPS with center-tape
✨ Teacher's Tip: If you have access to a quality
SMPS (Switched-Mode Power Supply) with center-tape
output, it will work perfectly! Many modern designers prefer SMPS for
their energy efficiency and lower heating.
This amplifier is quite tolerant regarding supply voltage,
operating normally at any value between 35V and 55V.
Naturally, the higher the voltage, the greater the output power, but with a
trade-off: increased thermal dissipation in the output transistors.
Recommendation: Use the recommended values to achieve
maximum performance with optimized thermal stability.
Before starting assembly, make sure you have
all components on hand. The table below presents the
complete and detailed list of all items needed to build
this 100W RMS amplifier.
To ensure your project is an absolute success, we've compiled the most
common questions about this amplifier. If your question isn't here, leave a
comment at the end of the article!
What is the difference between using two 2SC5200 (NPN) and a
complementary pair 2SC5200/2SA1943?🔽
The complementary configuration (NPN/PNP) is the
standard in professional amplifiers, offering better symmetry and lower
distortion. This project uses
two NPNs at the output for
educational and experimental purposes, allowing you to
compare different topologies and understand their limitations. Despite
being less traditional, it still offers satisfactory quality for home
and DIY use.
Can I use an asymmetrical (simple) power supply instead of a
symmetrical one?🔽
Not recommended. This circuit was specifically
designed for symmetrical power supply (±45V). Using an
asymmetrical (simple) supply will cause
significant distortion, reduced power and possible
damage to the transistors. If necessary, you can adapt the supply
voltage within the range of ±35V to ±55V, but symmetry is
essential.
What is the actual power the amplifier will deliver?🔽
With the recommended supply of ±45V and 5A, you will
get approximately 100W RMS on a 4Ω or 8Ω load. If you
use ±55V, the power will increase; if you use ±35V, it will decrease.
Power also depends on the load impedance (speaker).
Lower impedance values result in more power, but require larger heat
sinks.
The transistors get very hot. How can I avoid this?🔽
This is normal! The output transistors (Q1 and Q2)
always dissipate heat in an amplifier. To reduce this
problem: 1) Use
adequate aluminum heat sinks; 2) Apply
quality thermal paste between the transistor and heat
sink; 3) Maintain air flow (fan if
necessary); 4) Reduce
volume and continuous operation time during
testing.
Can I replace the 2SC5200 transistors with other power transistors?🔽
Yes, but with care! Equivalent transistors like
2SC3281, 2SC2500, MJL3281A may work, but it's essential
to check current gain (β),
maximum voltage (Vceo) and
dissipation (Ptot). Use our
data crossing tool
to ensure compatibility. Untested components may damage the
circuit.
The amplifier has noise or microphonics. How do I fix this?🔽
Tips to eliminate noise:1) Use
shielded cables for audio input;
2) Keep the board
away from RF sources (WiFi, cell phones);
3) Check if all
decoupling capacitors (C6, C8) are well soldered;
4) Test with an input potentiometer to
reduce gain; 5) If the problem persists, it may be
transistor microphonics—try using larger heat sinks or
thermally insulating the board.
I need to mount this amplifier in a case. What are the recommended
dimensions?🔽
There are no fixed dimensions, but we recommend a case with
at least 25cm × 20cm × 15cm to accommodate the PCB,
transformer and heat sinks. Important: Reserve space
for ventilation (air holes at the front and back) and
consider thermally isolating the transformer from the PCB. The PCB
itself is approximately 20cm × 12cm (depending on the
layout). You will find the exact dimensions in the files included in the
download.
🖨️ Printed Circuit Board (PCB)
To make your life easier, in Figure 4, we provide the
PCB files - Printed Circuit Board. The files are in GERBER, PDF and PNG formats, covering all your
needs, whether for a homemade assembly or to send to a professional
manufacturing.
And best of all: the files are available for
free download directly from the MEGA server, through a
direct link, without any complication or redirection!
Fig. 3 - PCB 100W RMS Power Amplifier 2 x 2SC5200 Output Transistors
📥Direct Link to Download
To download the necessary files for assembling the electronic circuit,
just click on the direct link provided below:
💡 Tip: If you plan to have
the PCB manufactured in a factory (JLCPCB, PCBWay,
etc.), use the Gerber files included in the download.
They contain all the necessary specifications for professional
production.
🎧 Already Built Your Amplifier? Share Your Experience!
We love to hear success stories! If you've assembled
this amplifier, test it and tell us in the comments:
🎵 How did the sound turn out? Any surprises?
⚙️ Did you make any modifications or adjustments?
📊 What was the actual power measured with a multimeter?
🐛 Did you find any problems? How did you solve them?
💡 Do you have suggestions to improve the project?
👇 Leave a comment below! We'll be happy to respond. 👇
🚀 Conclusion
This amplifier is an excellent starting point for those who want to
delve deeper into analog electronics. With each test and modification,
you'll learn more about how components behave in power circuits.
✨ Our Gratitude and Next Steps
We sincerely hope this guide has been useful and enriching for your
projects! Thank you for dedicating your time to this content.
Your Feedback is Invaluable:
Have any questions, suggestions, or corrections? Feel free to share them in
the comments below! Your contribution helps us refine this content for
the entire ElCircuits community.
If you found this guide helpful, spread the knowledge!
We currently have this one that delivers about 80W at the extreme with a single supply, and with only 3 transistors. https://www.elcircuits.com/2021/03/simple-3-transistors-power-amplifier.html
Sir, please PCB design diagram for this schemetic. Please.
ReplyDeleteHi Jagmal singh!
DeleteThe download section is just below the bill of materials, it is a direct download from MEGA.
Regards!
U r all projects r good
ReplyDeleteHello PARSHANT SHARMA!
DeleteThank you very much.
Best regards.
Do u have any single suppy 100w amplifier circuit diagram
ReplyDeleteHello Parshant sharma!
DeleteWe currently have this one that delivers about 80W at the extreme with a single supply, and with only 3 transistors.
https://www.elcircuits.com/2021/03/simple-3-transistors-power-amplifier.html
Best regards!