| With a small size, high efficiency, low distortion and high power characteristics, the Class D audio power amplifier possesses more broader developmental foreground. We can apply it to portable electronics such as MP3, CD, DVD players and notebook personal computer.The paper has designed a Class D audio power amplifier for portable audio electronics. First of all, I introduce the various kinds of power amplifiers, to analyze advantages and disadvantages of them, and then analyze Class D power amplifier in detail to improve its properties, such as stability, power supply rejection ratio, total harmonic distortion plus noise, and so on. On the basis of comprehensive consideration on power, area and performance, we has done a detailed analysis, design and simulation, including the bandgap reference, the fully differential operational amplifier, comparators, triangle-wave oscillator, driver circuit, power output circuit, over-current protection circuit and over-temperature protection circuit, and so on. Using feedback to improve the system of linearity and power supply rejection characteristics; using fully-bridge output to improve the output power and total harmonic distortion performance; using inductive speaker to achieve the restoration of the audio signal, and to save the cost and size.The design is implemented with SMIC 0.35μm 2P2M process. The layout and simulation are finished by Cadence. Finally, it supplies system application circuits and complete the chip test of Class D audio power amplifier. The results of chip test show that when the power supply is 5V,the chip has PSRR of 70dB at 217Hz, CMRR of 65dB at 217Hz, output power of 1.32W, power efficiency of about 82%, THD+N less than 1%. The results meet the specifications of design. |
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