LM1877M-9

LM1877M-9 Application Field and Working Principle

The LM1877M-9 is a high performance audio amplifier with monolithic integrated circuit developed by National Semiconductor Company. It is specifically designed for low power amplifier application fields, such as portable electronic devices. It includes a power amplifier and a linear amplifier stage, enabling both high-density integration and better sound quality. Its main application field are in both domestic and automotive audio systems.

The LM1877M-9 has a wide input voltage range, from 3V to 18V, which makes it suitable for most audio systems. It has low distortion rate of 0.002%, THD+N (total harmonic distortion noise). It also features low power dissipation of 1.2W and 0.8W in Idle and Full-Power, respectively. It has a wide frequency range of 20Hz to 20kHz with a signal-to-noise ratio of up to 80dB.

The working principle of LM1877M-9 utilizes the feedback loop to topologically adjust the output signal characteristics. It consists of two parts: the voltage amplifier stage (VAS), and the output stage. The VAS is the main control of the amplifier’s performance. It changes the input signal voltage into a suitable voltage for the output stage. The gain of VAS mainly depends on the resistor-capacitor network. The output stage is a single-ended Class AB amplifier with high efficiency and power output.

The VAS amplifies the signal voltage and conditions it for the output stage. The output stage amplifies the signal voltage according to the voltage of the VAS stage gain, and is designed to generate an adequate power with a low distortion rate. It can easily reach the full power output and bring little power consumption from the power supply. The frequency response of the LM1877M-9 is quite flat, and can accurately reproduce sound signals within the human audible range.

The LM1877M-9 is ideally suited for both MP3 players and home audio systems. Its miniature size makes it portable and suitable for MP3 players. It is also suitable for low power home audio system, such as radios and portable speakers. It extends to automotive audio system, such as car stereos, door systems, and other space-limited or low power electronic devices. It is a perfect solution for audio design engineer due to its flexible mechanical design, miniature size, and high performance.