| The three kinds of classic Audio Power Amplifier is class A, class B, class AB. These three kinds of linear Audio Power Amplifier have their own advantages. But they have a common drawback that the efficiency is less than 50%, this will reduce the overall system battery lifetime and increase the heat dissipation. With the development of Multimedia-Portable electronic products, high efficiency, small area Audio Power Amplifier is needed, so Class-D Audio Power Amplifier is used instead of the classic Audio Power Amplifier.In this paper, a low THD,high PSRR class d power amplifier is presented. Pulse width modulation with amplitude 1V, frequency 300KHZ,nonlinearity 1‰double- sided sawtooth carrier is used; it consists of Previous OPAMP, Triangle-Wave Oscillator, PWM Comparator, Deglitch-Protect Circuit, Power Output Circuit and Short Protect Circuit. This power amplifier can work with 2.5V-5.5V supply, and provide 2W rated output-power with 4ΩAudio-Load. The Total Harmonious Distortion (THD) is less than 0.08% and PSRR is 87dB at 217HZ.The design of each block is described in detail, simulation waves and THD are presented accurately, and PSRR is calculated approximately. The power amplifier is designed with 0.6um CMOS process, The layout area of the power amplifier chip is 2.1mm×2.1mm. |
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