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LM3886 amplifier circuit

2015-01-02 17:54  
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Posted by P. Marian in Audio | 11 comments
More projects with:Audio amplifier • LM3886

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lm3886 packageThe LM3886 is a high performance 150W Audio Power Amplifier with Mute. The performance of the audio power LM3886, say NS, utilising its Self Peak Instantaneous Temperature (°Ke) (SPIKe) protection circuitry, puts in a class above discrete and hybrid amplifiers by providing an inherently,dynamically protected Safe Operating Area (SOA).

The LM3886T comes in an 11 (staggered-) lead non-isolated TO220 package. For test purposes, the prototype of the amplifier was powered by a stabilised ±35-V supply. A maximum undistorted output power of about 63 watts into 8 ohms was obtained at a drive level of 1 Vrms. Dropping the load impedance to 4 ohms pushed the output power to no less then 108 watts. In practice, these power levels can be taken to mean ‘music power’, but do remember that the amplifier will not normally be powered from a regulated supply!

LM3886 amp circuit diagram

The circuit needs a well regulated and filtered 28V dual power supply.If you need some more punch extend the supply voltage up to 35V.Switch S1 is used for mute function, open it to mute the amplifier.

LM3886 circuit version 1
lm3886 amp
LM3886 schematic version 2
Build the amplifier following the schematic and PCB. As always, when testing it, test with a cheap speaker that damage to will not cost much to replace.
If your source is consistantly connected (ex. a pre-amp always connected to the amplifier), you can skip C2 by soldering a jumper in place of it on the PCB. If possible I would highly reccomend doing this to decrease signal path and increase audio quality. However, if your source may ever get disconnected (such as a CD player), it is reccomended that you include C2. If you do not, disconnecting the source will send a large DC current into the speaker and will very likely damage it. (from)
lm3886 amp
LM3886 PCB circuit version 3
lm3886 circuit
lm3886 pcb
LM3886 BTL stereo amp PCB (top & bottom) version 4from
The LM3886 bridge circuit is in a non-inverted configuration, so the input impedance is determined by the input resistor R1, i.e. 47k. The 680 ohm and 470pF resistor capacitor filter network is used to filter out the high frequency noise at the RCA input. The 220pF C4 and C8 capacitors are used to shot out the high frequency noise at the LM3886 input pins.
lm3886 schematic
The PCB is designed in a way that the power ground is separated from the signal ground, as you can see from the below layout. The signal ground is located in the middle and surrounded by the power ground. There is a thin trace near C5 connecting them. The PCB layout is done by using PADS PowerPCB 5.0. I think it is a powerful layout software.
lm3886 pcb top
lm3886 pcb bottom

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