A 16-$\Omega$ Audio Amplifier With 93.8-mW Peak Load Power and 1.43-mW Quiescent Power Consumption

A low-distortion three-stage class-AB audio amplifier is designed to drive a 16-Ω headphone speaker load. High power efficiency is achieved using fully differential internal stages with local common-mode feedback and replica biasing of the output stage. The threshold voltage of nMOS transistors was made comparable to that of pMOS transistors by negatively biasing the p-substrate in order to achieve high linearity. Multiple compensation networks guarantee the stability of the audio amplifier when driving a wide range of capacitive loads from 10 pF to 5 nF. Peak power delivered to the load is measured as 93.8 mW (corresponding to 46.9 mW RMS) with -77.9-dB total harmonic distortion; quiescent power is only 1.43 mW. The power-supply rejection ratio from both ±1.5-V supplies exceeds 63 dB over the entire audio frequency range. The design is implemented in a 0.5-μm CMOS process and occupies 0.34 mm2 of area.

[1]  Gaetano Palumbo,et al.  Feedback Amplifiers: Theory and Design , 2002 .

[2]  Gaetano Palumbo,et al.  Design guidelines for reversed nested Miller compensation in three-stage amplifiers , 2003, IEEE Trans. Circuits Syst. II Express Briefs.

[3]  T. Hartig,et al.  A high signal swing Class AB earpiece amplifier in 65nm CMOS Technology , 2006, 2006 Proceedings of the 32nd European Solid-State Circuits Conference.

[4]  Jong-Tae Hwang,et al.  1 W 0.8 /spl mu/m BiCMOS adaptive Q-current controlled class-AB power amplifier for portable sound equipments , 2002, 2002 IEEE International Solid-State Circuits Conference. Digest of Technical Papers (Cat. No.02CH37315).

[5]  Johan H. Huijsing,et al.  Frequency Compensation Techniques for Low-Power Operational Amplifiers , 1995 .

[6]  R. Becker,et al.  An audio amplifier providing up to 1 Watt in standard digital 90-nm CMOS , 2006, IEEE Journal of Solid-State Circuits.

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

[8]  R. Jacob Baker,et al.  CMOS Circuit Design, Layout, and Simulation , 1997 .

[9]  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.

[10]  S P Willig.  Operational amplifiers. , 1993, Biomedical instrumentation & technology.

[11]  Ka Nang Leung,et al.  Analysis of multistage amplifier-frequency compensation , 2001 .

[12]  Johan H. Huijsing,et al.  Operational Amplifiers - Theory and Design , 2000 .

[13]  Annajirao Garimella,et al.  Adaptive biasing technique to convert pseudo-class AB amplifier to class AB , 2010 .

[14]  Filippo Neri,et al.  A Class-AB/D Audio Power Amplifier for Mobile Applications Integrated Into a 2.5G/3G Baseband Processor , 2010, IEEE Transactions on Circuits and Systems I: Regular Papers.