The Design Of An Audio Power Amplifier For The Car

A new-type of fourfold audio power amplifier has been designed for the car electron multimedia system in this paper, and it has been designed as an audio power amplifier with the features of high power and high efficiency. This chip can supply 42W power, which has class-AB output stage, and with Miller compensation internal to guarantee the stability of close loop.This audio power amplifier has internal current limit,thermal shutdown and over-voltage protection circuit. When it is delivering high output power to the load or driving nonlinear reactive loads, the degradation of the output transistor or catastrophic failure of the whole circuit may happen without those internal protection circuits. In addition, the proper mute bypassing is critical for POP noise performance on power. The design takes advantage of advanced circuit techniques and process technology to achieve extremely low distortion levels even at high output power. The chip also has the following features: open loop gain of 115dB, current capability of 4A, and so on.The chip is made up of the bias circuits, input stage, output stage, protect circuit, common-mode amplifier (CMA) and capacitance (ICM) module. According to the electricity characteristics of the chip, circuit structure of each module is analyzed. Based on the 2μm 36V Bipolar high technology of the BCD company and combining the characteristics and requirement of Bipolar Cadence, each module and whole circuit are simulated by Candence, the result is that offset voltage is 0.538 mV, phase margin is 50°, harmonic distortion is 0.5%, voltage power source rejection ratio is -70dB and the efficiency is 58.1%. The results show that the chip meets the design requirements.