A filter free class D audio amplifier with 86% power efficiency Muggler, P., Chen, W., Jones, C., Dagli, P., Yazdi, N., ISCAS '04. Proceedings of the 2004 International Symposium on Circuits and Systems, Volume 1, May 2004 pp.I Vol.1 指導老師：易序忠 學 生：楊正元 國立彰化師範大學積體電路設計研究所

Outline  Abstract  Schematic  Result

Abstract  2.5W output power and 86 ％ efficiency with an 8 ohm load.  It operates with a 2.5 V to 6.5 V supply voltage in a 7V, 1.2 um, double-poly, triple-metal, BiCMOS process.  It has an area of 1.5 x 1.5 mm 2 and it achieves a THD as low as 0.04%, with a flatband response between 20 Hz and 20 kHz.

Modulation Scheme  Double-sided natural sampling pulse width modulation scheme.  The selected PWM scheme provides current to the load only when needed, and once delivered the current is maintained. This is accomplished by using all four states available to a full H-bridge. The modulation scheme uses any of the states in any order, dependent upon the audio input signal.

Different kinds of PWM modulations

Advantage  The amount of information contained in each period is twice the amount of single sided modulation.  There is the possibility of having all of the significant distortion components to be outside the audio band thus enabling a filter free class D audio amplifier.

Signal Spectrum showing Distortion Components

Schematic of the Designed Class D Audio Power Amplifier

Cross-Coupling

Example

Efficiency versus Power Curve

Total Harmonic Distortion versus Power Curve

Die Photo

SUMMARY OF MEASUREMENT RESULTS

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