A High-Power Class D Audio Amplifier

Mohammad Adeel, Farah Shariff, BoQiang Xiao

We are designing a Class D audio power amplifier for use in driving conventional 8Ohm speaker loads.  A class D amplifier is a type of high efficiency amplifier used in portable audio applications where battery life is of critical importance to the product. Conventional class AB audio amplifiers are around 60-70% efficient, where as class D architectures are up to 90% efficient. This is possible due to the fact it is a switching amplifier, spending much less time dissipating power in the high gain region of operation. Here, output stage feedthrough causes most of the dynamic power loss in conventional amplifiers. We plan on designing the class D amplifier with external resistor gain control, feedback error compensation, AD modulation, and external oscillator input. We aim to integrate the high power output stages on chip while achieving over 0.5W output power when driving an 8Ohm speaker. We will optimize for efficiency and THD.

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