| Summary: | 碩士 === 國立臺灣大學 === 電機工程學研究所 === 99 === Applications of the delta-sigma modulator in digital and analog circuits are discussed in this thesis. Delta sigma modulator can be used in digital circuits such as digital-to-analog converters and fraction-N frequency synthesizers; or in analog circuits such as analog-to-digital converters, DC-DC converters and switched-mode power amplifiers. According to these applications, a digital modulator for fractional divider and an analog modulator for nonlinear switched-mode power amplifier are proposed in the thesis.
We can decrease locking time and reduce channel bandwidth by applying fractional divider in fractional-N frequency synthesizers. Therefore, a digital MASH 1-1-1 modulator based on the carry-look-ahead adder which can integrate with multi-modulus divider to realize the fractional division function is designed and presented in this thesis.
Class-D power amplifiers have been widely used as the audio amplifiers in portable devices. The greatest advantage is the high power efficiency of this kind of amplifier, which can improve the operating time and lower the heat dissipation. Nevertheless, the total harmonic distortion in nonlinear amplifiers is much higher than the linear ones. Therefore, the applications of the nonlinear amplifiers are limited to lower-quality audio systems. A class-D audio amplifier system based on a third-ordered analog delta-sigma is proposed and designed in this thesis.
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