300W Power Amplifier with LM3886 Bridge-Parallel Configuration

The project is based on six LM3886 to produce a well designed audio power amplifier that is capable of delivering pure 300W on 4 Ohm speakers.

Each of the 2 boards of 3 x LM3886 such as PA150 are bridged together using the DRV134 which explains the main design concept as the amplifier is configured in push-pull topology with a doubled total gain of the amplifier. Converting the unbalanced input signal to a balanced signal is the function of DRV134. This makes the non-inverted signal to be fed to one PA150 and the inverted signal fed to another PA150. Connected to the speaker’s positive input is one of the PA150 with the other PA150 to the negative.

To be able to use a trim pot to adjust the DC offset of each 3886, the LM3886 was used in the inverted configuration. The DC offset of each 3886 can be made to about 9mV after some adjustment since this is a push-pull configuration which makes the DC offset at speaker terminal very close to 0mV. Using an aluminum bar, the 3886s are mounted to the heatsink with more pressure for better heat transfer.

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