Ripple Feedback Filter Suitable for Analogmigital Mixed-Mode Audio Amplifier for Improved Efficiency and Stability
نویسندگان
چکیده
A new ripple feedback filter is presented for Analog/Digital mixed-mode amplifier (MMA) among audio applications. MMA is composed of two amplifiers: one is analog amplifier responsible for high fidelity and the other is digital switching amplifer in charge of high efficiency. To improve both total harmonic distortion (THD) and efficiency, passive RLC filter is needed at the output side of the digital switching amplifier. Conventional filter, however, causes phase delay, which worsens current loop stability and makes the normal operation of MMA impossible. Ripple feedback filter is newly suggested to solve this problem, obtaining excellent efficiency and low THD. amplifier is in charge of high efficiency and works as a dependent current source to supply most of the current needed in the load. The principle of operation is very simple and clear. There exist two switching states in digital amplifier. The first state is M1 (PMOS) turn-on and M2 (NMOS) turn-off state. The second switching state is vice versa.
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