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68W Hi-Fi Audio Power Amplifier - IC LM3886T + PCB


Fig. 1 - PCB  68W Hi-Fi Audio Power Amplifier - IC LM3886T

The LM3886 is a high-performance audio power amplifier capable of delivering 68W of continuous average power to a load and 38W into with 0.1% THD+N from 20Hz–20kHz

The performance of the LM3886, utilizing its Self Peak Instantaneous Temperature (°Ke) (SPiKe) protection circuitry, puts it in a class above discrete and hybrid amplifiers by providing an inherently, dynamically protected Safe Operating Area (SOA)

SPiKe protection means that these parts are completely safeguarded at the output against over-voltage, under-voltage, over-loads, including shorts to the supplies, thermal runaway, and instantaneous temperature peaks. The IC pinout is shown in Figure 2 below.
Fig. 2 - Pinout IC LM3886T

The LM3886 maintains an excellent signal-to-noise ratio of greater than 92dB with a typical low noise floor of 2.0μV. It exhibits extremely low THD+N values of 0.03% at the rated output into the rated load over the audio spectrum, and provides excellent linearity with an IMD (SMPTE) typical rating of 0.004%.

Features

  • 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
  • An Input Mute Function
  • Output Protection from a Short to Ground or to the Supplies via Internal Current Limiting Circuitry
  • Output Over-Voltage Protection against Transients from Inductive Loads
  • Supply Under-Voltage Protection, not Allowing Internal Biasing to Occur when |VEE| + |VCC| ≤ 12V, thus Eliminating Turn-On and Turn-Off Transients
  • 11-Lead TO-220 Package

The Power Supply

The power supply is Symmetrical, for those who will use a 4Ω Loudspeaker, the 2x 20Vac transformer is recommended, because when rectified, it is around 28Vdc, and for those who will use it at 8Ω, it is recommended the 2x 25Vac transformer, which when rectified, is 35Vdc on average.

The recommended transformer power is about 120W, this means that the transformer current is on average 3.5 Amperes, for mono, if it's stereo, do the duplication, that is, 8 Amperes. 

A good size heat radiator is necessary, since the IC LM3886 works in class AB, there is a great loss in heat at full power, and the recommended filter capacitors is 2 x 10.000uF/50V

The output inductance is formed by 15 turns of enameled wire, with a diameter of approximately 0.5mm, wound around the resistor R8 of 10Ω 1W. The complete schematic diagram is shown in Figure 3 below.

Fig. 3 - Schematic  68W Hi-Fi Audio Power Amplifier - IC LM3886T

Components List

  • U1 .......................... LM3886 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 ................... Block 5mm 2 Pin weldable terminal Connector
  • P3 ......................... Block 5mm 3 Pin weldable terminal Connector
  • Others ................... Printed Circuit Board, Wires, Solders and Etc.
We are offering the PCI - Printed Circuit Board, in GERBER, PDF and PNG files, for you who want to do the most optimized assembly, either at home, or if you prefer in a company that develops the board, you can is downloading and make the files in the Download option below.

Files to Download, Direct Link:

Click on the link beside: GERBER, PDF and PNG files


Any questions, suggestions, corrections, please leave them in the comments below, which we will soon be answering.

My best Regards to You!!!


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