Hello Electronics Enthusiasts!
If you're looking for an audio amplifier that combines high power, excellent fidelity, and ease of assembly, the project we're presenting today is the perfect choice! The LM3886T is a high-performance audio amplifier integrated circuit capable of delivering 68W of continuous average power to a 4Ω load and 38W into 8Ω with just 0.1% THD+N across the entire audio range of 20Hz to 20kHz.
🌟 What Makes the LM3886T Special?
The performance of the LM3886T, utilizing its Self Peak Instantaneous Temperature (°Ke) (SPiKe) protection circuit, places it in a class above discrete and hybrid amplifiers, providing an inherently and dynamically protected Safe Operating Area (SOA).
The SPiKe protection means these components are fully protected at the output against overvoltage, undervoltage, overloads, including short circuits in the power supplies, thermal runaway, and instantaneous temperature spikes. The IC pinout is shown in Figure 2 below.
The LM3886T maintains an excellent signal-to-noise ratio greater than 92dB with a typically low noise floor of 2.0μV. It exhibits extremely low THD+N values of 0.03% at the rated output into the rated load across the entire audio spectrum, and provides exceptional linearity with a typical IMD (SMPTE) rating of 0.004%.
Technical Features of the LM3886T
- 68W cont. avg. output power into 4Ω at VCC = ±28V
- 50W cont. avg. output power into 8Ω at VCC = ±35V
- 38W cont. avg. output power into 8Ω at VCC = ±28V
- 135W Instantaneous Peak Output Power Capability
- Signal-to-Noise Ratio ≥ 92dB
- Input Mute Function
- Output Short-Circuit Protection to Ground or Supplies via Internal Current Limiting Circuit
- Output Overvoltage Protection against Inductive Load Transients
- Power Supply Undervoltage Protection, Not Allowing Internal Biasing when |VEE| + |VCC| ≤ 12V, Eliminating Turn-On and Turn-Off Transients
- 11-Pin TO-220 Package
⚡ Power Supply: The Heart of the Amplifier
The power supply is Symmetrical, essential for the proper operation of the amplifier. For those using a 4Ω speaker, the 2x 20Vac transformer is recommended, as when rectified, it results in approximately 28Vdc.
For those using 8Ω, the 2x 25Vac transformer is recommended, which when rectified, results in 35Vdc on average.
The recommended power for the transformer is about 120W, which means the transformer current is on average 3.5 Amperes, for mono. If it's stereo, double it, i.e., 7 Amperes.
A good heat sink is essential, as the LM3886 IC operates in class AB, with significant heat loss at maximum power. The recommended filter capacitors are 2 x 10,000uF/50V to ensure a stable and ripple-free power supply.
🔌 Circuit Schematic Diagram
The output inductance is formed by 15 turns of enameled wire, with a diameter of approximately 0.5mm, wound around the 10Ω 1W resistor R8. This arrangement helps to stabilize the amplifier with reactive loads. The complete schematic is shown in Figure 3 below.
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🧾 Detailed Bill of Materials
- U1 ......................... LM3886T Integrated Circuit
- R1, R3 .................. 2.2K ohms - 1/8W - Resistor - (red, red, red, gold)
- R2, R4, R5, R6 ..... 47K ohms - 1/8W - Resistor - (yellow, violet, orange, gold)
- R7 ......................... 4R7 ohms - 1W - Resistor - (yellow, violet, gold, gold)
- R8 ......................... 10 ohms - 1W - Resistor - (brown, black, brown, gold)
- C1 ......................... 2.2uF - 25V - Electrolytic Capacitor
- C2 ......................... 680pF Polyester Capacitor
- C3 ......................... 470uF - 50V - Electrolytic Capacitor
- C4, C8 .................. 100nF - ceramic/polyester capacitor
- C5, C7 .................. 1000uF - 50V - Electrolytic Capacitor
- C6 ......................... 47pF - ceramic/polyester capacitor
- C9 ......................... 220nF - ceramic/polyester capacitor
- C10 ....................... 100uF - 50V - Electrolytic Capacitor
- L1 ......................... 0.7uH Inductor - *See Text
- P1, P2 ................... 2-Pin 5mm Solderable Connector Block
- P3 ......................... 3-Pin 5mm Solderable Connector Block
- Others .................. PCB, Heat Sink, Wires, Solder and etc.
🖨️ Printed Circuit Board (PCB)
We are providing for Download all the necessary materials for those who want to assemble with the suggested board: files in PNG, PDF for home printing and Gerber files for those who want to send for professional manufacturing.
📥 Download the Project Files Now!
To download the necessary files to assemble the electronic circuit, just click on the direct link provided below:
Download Link: GERBER, PDF and PNG Files
🤔 Frequently Asked Questions (FAQ)
To ensure your project is a success, we've compiled some of the most common questions about this amplifier. Check them out!
What is the difference between the LM3886 and the LM3886T? 🔽
The LM3886T is the fully electrically insulated version of the LM3886. The "T" indicates that the IC has more robust thermal insulation, allowing direct mounting to the heat sink without the need for insulating mica between the IC and the heat sink. Both have the same electrical and performance characteristics.
Can I use this amplifier for subwoofers? 🔽
Yes, the LM3886 works very well in subwoofer applications due to its excellent low-frequency response and high power. However, for specific subwoofer applications, you may want to slightly modify the circuit to optimize the frequency response, adjusting the values of C2 and C6.
What is the minimum recommended heat sink size? 🔽
The ideal heat sink should have a maximum thermal resistance of approximately 1.4°C/W for operation at 4Ω with music signals. For continuous operation at maximum power, an even larger heat sink is recommended. Quality thermal paste is essential to ensure good heat transfer from the IC to the heat sink.
How can I turn this amplifier into a stereo system? 🔽
To create a stereo system, you will need to assemble two identical circuits, one for each channel. The power supply should be sized to provide double the current (approximately 8A instead of 4A). You can use a single more robust symmetrical power supply or two identical power supplies, one for each channel.
Is it possible to add volume and tone controls to this circuit? 🔽
Yes, you can add a volume control (10kΩ logarithmic potentiometer) at the signal input, before capacitor C1. For tone controls (bass and treble), you can implement an active or passive Baxandall circuit before the amplifier input. There are various preamplifier circuits that can be easily integrated into this project.
👋 I hope you enjoyed it!!!
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