Intrinsic distortion of a fully differential BD-modulated Class-D amplifier with analog feedback

Cox, Stephen M.; Yu, J.; Goh, W.L.; Tan, M.T.

Abstract

This paper presents a mathematical analysis of a fully differential BD-modulated Class-D amplifier with analog feedback, i.e., one having a bridge-tied-load output configuration with negative feedback and ternary PWM signal. Notwithstanding the highly nonlinear nature of
the amplifier's operation, an extremely accurate closed-form expression for the audible output signal is derived and verified based on computer simulations. This expression demonstrates that there exist larger
high-order intrinsic distortions (e.g., 5th-order harmonic distortion and intermodulation distortion) for BD-modulation, compared to that for AD-modulation (binary PWM signal). Furthermore, the 3rd-order harmonic
distortion has a roughly parabolic response as a function of the magnitude of the input signal and reaches its peak when the modulation index of the input signal is around 0.7. Overall, the BD-modulated Class-D amplifier has a larger intrinsic distortion for small input signal but a smaller intrinsic distortion for large input signal,
compared to AD-modulated designs.

Citation

Cox, S. M., Yu, J., Goh, W., & Tan, M. (2013). Intrinsic distortion of a fully differential BD-modulated Class-D amplifier with analog feedback. IEEE Transactions on Circuits and Systems I: Regular Papers, 60(1), https://doi.org/10.1109/TCSI.2012.2215713

• Journal Article Type: Article
• Publication Date: Jan 1, 2013
• Deposit Date: Feb 9, 2013
• Publicly Available Date: Feb 9, 2013
• Journal: IEEE Transactions on Circuits and Systems I: Regular Papers
• Print ISSN: 1549-8328
• Electronic ISSN: 1558-0806
• Publisher: Institute of Electrical and Electronics Engineers
• Peer Reviewed: Peer Reviewed
• Volume: 60
• Issue: 1
• DOI: https://doi.org/10.1109/TCSI.2012.2215713
• Public URL: https://nottingham-repository.worktribe.com/output/1003780
• Publisher URL: http://dx.doi.org/10.1109/TCSI.2012.2215713
• Additional Information: (c) 2013 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other users, including reprinting/ republishing this material for advertising or promotional purposes, creating new collective works for resale or redistribution to servers or lists, or reuse of any copyrighted components of this work in other works.