A Low Power Class-AB Audio Power Amplifier With Dynamic Transconductance Compensation in 55 nm CMOS Process

This paper presents a Class-AB audio power amplifier with state-of-the-art power efficiency and performance. In this work, the second stage transconductance of the three-stage power amplifier can be dynamically compensated, in order to automatically adjust the amplifier pole according to the operating condition of the output stage. Working with a current sensing module, the proposed dynamic transconductance compensation scheme is more power-efficient to allocate the frequency of non-dominant-pole under a specified stability requirement. A prototype chip is designed and fabricated using 55 nm CMOS process. The measured static current consumption of the core circuit is 0.35 mA with a 1.8 V supply voltage. -85 dB THD+N, 106 dB signal dynamic range and 55 mW output power are verified in silicon under a wide range of load capacitance from 5 pF to 20 nF. Measurement result shows the proposed transconductance compensation technique is effective in both constant voltage supply mode and dynamic supply (Class-G) mode.

[1]  Edgar Sánchez-Sinencio,et al.  Design of Three-Stage Class-AB 16 $\Omega$ Headphone Driver Capable of Handling Wide Range of Load Capacitance , 2009, IEEE Journal of Solid-State Circuits.

[2]  Man-Kay Law,et al.  Correction to "A 0.016 mm2 144-µW Three-Stage Amplifier Capable of Driving 1-to-15 nF Capacitive Load With >0.95-MHz GBW" , 2013, IEEE J. Solid State Circuits.

[3]  Jianlong Chen,et al.  A 62mW stereo class-G headphone driver with 108dB dynamic range and 600µA/channel quiescent current , 2013, 2013 IEEE International Solid-State Circuits Conference Digest of Technical Papers.

[4]  Angelo Nagari,et al.  An 8 $\Omega$ 2.5 W 1%-THD 104 dB(A)-Dynamic-Range Class-D Audio Amplifier With Ultra-Low EMI System and Current Sensing for Speaker Protection , 2012, IEEE Journal of Solid-State Circuits.

[5]  Ahmet Tekin,et al.  A 40 nm Fully Integrated 82 mW Stereo Headphone Module for Mobile Applications , 2014, IEEE Journal of Solid-State Circuits.

[6]  G.C. Temes,et al.  A 0.8V, 88dB Dual-Channel Audio /spl Delta//spl Sigma/ DAC with Headphone Driver , 2006, 2006 Symposium on VLSI Circuits, 2006. Digest of Technical Papers..

[7]  K. Gopakumar,et al.  A Five-Level Inverter Topology with Single-DC Supply by Cascading a Flying Capacitor Inverter and an H-Bridge , 2012, IEEE Transactions on Power Electronics.

[8]  Kuo-Hsin Chen,et al.  A High-PSRR Reconfigurable Class-AB/D Audio Amplifier Driving a Hands-Free/Receiver 2-in-1 Loudspeaker , 2012, IEEE Journal of Solid-State Circuits.

[9]  B.K. Ahuja,et al.  An improved frequency compensation technique for CMOS operational amplifiers , 1983, IEEE Journal of Solid-State Circuits.

[10]  Hui Zheng,et al.  A 60 mW Class-G Stereo Headphone Driver for Portable Battery-Powered Devices , 2012, IEEE Journal of Solid-State Circuits.

[11]  Angelo Nagari,et al.  An 8Ω 2.5W 1%-THD 104dB(A)-dynamic-range Class-D audio amplifier with an ultra-low EMI system and current sensing for speaker protection , 2012, 2012 IEEE International Solid-State Circuits Conference.

[12]  C. Mohan,et al.  A 16-$\Omega$ Audio Amplifier With 93.8-mW Peak Load Power and 1.43-mW Quiescent Power Consumption , 2012, IEEE Transactions on Circuits and Systems II: Express Briefs.

[13]  Ka Nang Leung,et al.  Nested Miller compensation in low-power CMOS design , 2001 .

[14]  Juing-Huei Su,et al.  Integrated Class-D Amplifier With Active Current Sensing Suitable for Alternating Current Switches , 2008, IEEE Transactions on Industrial Electronics.

[15]  Mohammad Yavari.  Hybrid Cascode Compensation for Two-Stage CMOS Opamps , 2005, IEICE Trans. Electron..

[16]  L.E. Larson,et al.  A capacitance-compensation technique for improved linearity in CMOS class-AB power amplifiers , 2004, IEEE Journal of Solid-State Circuits.

[17]  E. Fong,et al.  Analysis of harmonic distortion in single-channel MOS integrated circuits , 1982, IEEE Journal of Solid-State Circuits.

[18]  Marco Berkhout,et al.  A 4Ω 2.65W Class-D Audio Amplifier With Embedded DC-DC Boost Converter, Current Sensing ADC and DSP for Adaptive Speaker Protection , 2013, IEEE Journal of Solid-State Circuits.

[19]  Ka Nang Leung,et al.  Three-stage large capacitive load amplifier with damping-factor-control frequency compensation , 2000, IEEE Journal of Solid-State Circuits.

[20]  G.A. Rincon-Mora,et al.  Active capacitor multiplier in Miller-compensated circuits , 2000, IEEE Journal of Solid-State Circuits.

[21]  Zhang Weidong,et al.  Audio testing technology research , 2011, IEEE 2011 10th International Conference on Electronic Measurement & Instruments.

[22]  Willy Sansen,et al.  Nested feed-forward Gm-stage and nulling resistor plus nested-Miller compensation for multistage amplifiers , 2002, Proceedings of the IEEE 2002 Custom Integrated Circuits Conference (Cat. No.02CH37285).