LM4906 Audio Power Amplifier Circuit

As shown in the figure, this is a typical application circuit of the LM4906 audio power amplifier (MSOP package). After the audio signal is input, it is coupled to the inverting input terminal (pin 4) of the amplifier through C2. After power amplification, it is added to the speaker from Vo1 (pin 5) and Vo2 (pin 8) in the form of bridge output. There are two amplifiers inside the LM4906. The gain of the first amplifier can be controlled by the gain selection terminal (pin 3). When pin 3 is low, the gain is 6dB, and when pin 3 is high, the gain is 12dB. The gain of the second amplifier is fixed to 1 by two internal 20kΩ resistors. When the LM4906 outputs in the form of bridge differential, the gain Av of the power amplifier is 2×20kΩ/20kΩ or 2×40kΩ/20kΩ. When pin 1 is at a logic low level, the amplifier is micro-powered off, and when it is at a logic high level, the amplifier works at full power.