Inverting unity gain amplifier circuit composed of LM1877

As shown in the figure, it is an inverting unity gain amplifier circuit composed of LM1877. The audio signal is coupled through a 0.1μF capacitor and a 100kΩ resistor, added to the inverting input terminal 8 of LM1877, and output from pin 13 after amplification to the load resistor RL. The gain of the amplifier is determined by the ratio of the 100kΩ resistor at the input terminal to the 100kΩ resistor in the feedback loop between pins 13 and 8, so the amplifier gain is 1, which constitutes an inverting unity gain amplifier. The 2.7Ω resistor and 0.1μF capacitor connected in parallel with the output terminal 13 are used to filter out high-frequency noise.