A Novel 3D Filter-less Class-D Audio Amplifier with Stereo Enhancement

Abstract

This paper presents a novel 3D filter-less class-D audio amplifier with the stereo enhancement structure. The principle of this stereo enhancement scheme has been analyzed. It shows that the amplifier with this proposed circuit has a better live effect than the traditional class-D audio amplifiers. In this amplifier, the input audio signal from one channel can be amplified in two channels at the same time by way of cross-coupling. The ratio of gains in the two channels also can be adjusted by changing the external resistance, which improves the stereo effect. A practical implementation in the SMIC CMOS 0.18-μm process has been done to validate the theoretical results. When a sine signal with 1 kHz frequency and 100 mV amplitude is applied in one channel and a DC applied signal in the other, the amplifier demonstrates a gain difference of 9.4 dB. A double-sided natural sampling PWM is used in the proposed class-D amplifier to eliminate low-pass filter. The experimental result shows that the amplifier can deliver 2.5 W × 2 into 2 Ω loads at 3.3 V power supply and the THD + N is less than 0.1% without the external filters.

Keywords:

• Class-D amplifier
• Cross-coupling
• Filter-less
• Ratio of gains
• Stereo enhancement

Additional information

Notes on contributors

Lianxi Liu

Lianxi Liu received the M.S. and Ph.D. degrees in microelectronics from Xidian University, Xi’an, P.R. China in 2004 and 2006, respectively. He is currently an associate professor with the School of Microelectronics, Xidian University. His research interests include high-speed CMOS data converters, mixed-signal integrated circuits design, and low-voltage low-power analog circuits design. E-mail: [email protected] or [email protected]

Shijie Deng

Shijie Deng received the B.S. degree in microelectronics from Xidian University, Xi’an, P.R. China. He is currently working toward the M.S. degree at the School of Microelectronics, Xidian University. His research interests include deep submicron SoC design and mixed-signal integrated circuits design. E-mail: [email protected]

Yue Niu

Yue Niu received the B.S. degree in microelectronics from Xidian University, Xi’an, P.R. China. He is currently working toward the M.S. degree at the School of Microelectronics, Xidian University. His research interests include high-speed CMOS data converters and mixed-signal integrated circuits design. E-mail: [email protected]

Zhangming Zhu

Zhangming Zhu received the M.S. and Ph.D. degrees in microelectronics from Xidian University, Xi’an, P.R. China in 2001 and 2004, respectively. He is currently a professor with the School of Microelectronics, Xidian University. His research interests include electronic design automation, mixed-signal integrated circuits design, and 3D-ICs. E-mail: [email protected]

Yintang Yang

Yintang Yang received the B.S., M.S., and Ph.D. degrees in microelectronics at Xidian University and Xian Jiaotong University, Xi’an, China, respectively. He is now the Vice President of Xidian University, a professor and doctor director of integrated circuit design, VLSI, and microelectronics at Xidian University. His research interests include high-speed CMOS data converters, VLSI technology, deep submicron SoC design, new semiconductor materials and devices, and Network-on-Chip. E-mail: [email protected]