Dual power supply audio power amplifier circuit composed of LM3875

As shown in the figure, this is the dual-power supply audio power amplifier circuit of LM3875. The input signal VIN is added to the 7th pin of LM3875 through the potentiometer RIN, and after power amplification, it is output from the 3rd pin and added to the load resistor RL. When designing the printed circuit board, it should be noted that the load current return ground, output compensation ground and weak current ground should be routed separately, and the large current routing should be as far away from the input signal line as possible to prevent high-frequency self-excitation oscillation. If the electromagnetic wave generated by the output current is coupled to the input end through space to cause high-frequency self-excitation oscillation, a small capacitor of 50-500pF can be connected across the output end to eliminate the self-excitation. LM3875 has a thermal protection function. When the temperature rises to 165℃, the circuit is shut down, and when the temperature drops to 155℃, it starts to work again. The temperature then rises again, and it will be shut down again when it rises to 165℃ again. When using LM3875, the selection of heat sink should be based on the principle that the junction temperature is lower than the temperature protection starting point during operation, and the thermal resistance of the heat sink in contact with LM3875 should be small. The maximum power consumption of LM3875 is PD(MAX)=VCC2/(2π2RL). The average power consumption of LM3875 is PDAVE=(Vopk/RL)[Vcc/π-Vopk/2], where VCC is the total power supply voltage applied to LM3875; Vopk is the output peak voltage; and RL is the load resistance.