A class D amplifier with feedback after the LC filter

A class D system consists of a class D amplifier and an LC filter. To guarantee the best THD performance, both the class D amplifier and the LC filter must obtain optimal THD. LC filter exhibits poor linearity due to components non-linearity. By putting the LC filter in the feedback loop of the class D amplifier, its nonlinearity will be corrected. However, the LC filter contributes two-poles which makes loop stability a challenge. On top of that, the LC filter exhibits large component spread, which makes stability even more problematic. To mitigate this problem, the LC filter can be characterized during state-up. The information will then be used to adaptively adjust the loop filter coefficients of the class D amplifier during normal operation to ensure loop stability.

Contact

dr. (EI group) Qinwen Fan

Electronic Instrumentation Group

Department of Microelectronics

Last modified: 2019-10-02