This is a simple 20W bridge amplifier based on TDA7240A. This circuit is designed for car audio system, but you may use this circuit for your small home audio application… 
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Schematic Diagram:
This circuit operated with 18VDC asymmetrical power supply (positive (+) and ground only). Mount the power IC on a heatsink to prevent over heating.
PCB Layout:
About TDA7240A:
The TDA7240A is a 20W bridge audio amplifier IC designed specially for car radio applications. The low external component count and compact Heptawatt 7-pin power package the TDA7240A occupies little space on the printed circuit board.
Reliable operation is guaranteed by a comprehensive array of on-chip protection features. These include protection against AC and DC output short circuits (to ground and across the load), load dump transients, and junction over temperature. Additionally, the TDA7240A protects the loudspeaker when one output is short-circuited to ground.
Download TDA7240A datasheet for circuit reference.
TDA7240A Datasheet 1.17 MB
Download Datasheet