A good PCB layout for the TPA6205A1DGNR involves keeping the input and output traces short and away from each other, using a solid ground plane, and placing decoupling capacitors close to the device. TI provides a recommended layout in the datasheet and application notes.
The gain setting depends on the input signal level and the desired output power. The TPA6205A1DGNR has a fixed gain of 20 dB, but you can adjust the gain using external resistors. TI provides a gain calculation formula in the datasheet.
The maximum power dissipation of the TPA6205A1DGNR is dependent on the ambient temperature and the thermal resistance of the PCB. TI provides a power dissipation calculation formula in the datasheet, and recommends a maximum junction temperature of 150°C.
TI recommends using ESD protection diodes and overvoltage protection circuits to protect the TPA6205A1DGNR from electrostatic discharge and voltage surges. You can also use a voltage regulator to regulate the supply voltage.
TI recommends using a 10-µF capacitor in parallel with a 100-nF capacitor as close to the device as possible to decouple the power supply. This helps to filter out noise and ensure stable operation.