Abstract
In this thesis it designs a low-distortion, third-order feedforward sigma-delta modulator for digital audio system applications. This modulator is realized by switched-capacitor circuits, which belong to the structure of discrete type, and is suitable for low-to-medium, high resolution applications.Comparing it to conventional architecture, this structure not only reduce the numbers of 1-bit DAC feedback circuits, but also is suitable for operating in low-voltage environment. Finally it imports a zero optimization technique, which adds a feedback loop between second and third stage of modulator to increase performance. Since the design of high order system may be suffered from stability problem, system simulation by MATLAB is needed. First it builds ideal system model by SIMULINK, and then adds the non-ideal effects to original model in order to find out the corresponding circuit specifications to meet the system performance. As a result the circuits are implemented according to them so it reduces the time of HSPICE simulation. This modulator is implemented in TSMC 0.35um, 2P4M, CMOS technology. With the signal bandwidth of 20kHz and sampling rate of 5.12MHz, it can achieve 86dB SNDR and 98dB SFDR. In addition, the power dissipation is 12.27mW and the chip core size is 2.15mm2. With the zero optimization technique of modified circuit, the chip core size is 2.76mm2, and it can achieve 91dB SNDR and 104dB SFDR, which about 15-bit resolution, to meet the digital audio application without increasing extra power dissipation.