CD音樂為高音質音樂的標準之一，其取樣頻率為44.1K Hz且解析度有16位元。由於近年來對高音質音樂需求增加，所以應用於音頻之數位/類比轉換器所扮演的腳色也越來越重要。如何同時達到消費性電子產品的低成本需求、專業錄音用途所引頸期盼的高線性度、以及可攜式產品要求的低功率消耗，這將是極富挑戰的研究課題。
本篇論文設計應用於CD音樂品質，1位元超取樣三角積分調變系統中的數位/類比轉換器，並運用D類音頻放大器與低通濾波器，濾除雜訊、放大輸出來推動喇叭。本論文之電路分為數位及類比二部分，其中數位電路為一超取樣三角積分調變系統，由二個子系統組成，首先是負責升頻的數位內插式濾波器；再者為使用單迴路的數位三角積分調變器，其目的是為了要將量化雜訊推至高頻，並且將輸出轉量化為1位元。類比電路為一D類音頻放大器，使用半橋式方式進行設計改良，改良後可得與全橋式相同的總諧波失真，晶片外再以一主動式二階濾波器搭配喇叭之低通效果濾除頻寬外的雜訊。透過此系統來實現一個適用於低瓦數揚聲器，CD音樂品質的數位/類比轉換器。晶片使用TSMC 0.18um製程實現，晶片面積包含腳位約1.373mm2、功耗約為3.51mW、以1K Hz訊號輸入時之失真大小為-85dB。

CD-AUDIO is one of the high-quality audio standard that supports 16-bit linear pulse-code modulation (PCM) with sampling rate 44.1K Hz. Due to the increasing demand of high-quality audio, audio analog/digital converter (ADC) plays an important role nowadays. How to fit the the requirements, such as low-cost as a consumer electronic products, high linearity for professional recording, and low power consumption as a portable device are a challenging issues.
This paper implemented a system of 1-bit output delta sigma modulator (DSM) that works with a class D audio amplifier and a low-pass filter to form an ADC. The filter can suppress the out-of-band noise and amplifies the output to the speaker. The DSM consists of two parts: A digital Interpolation Filter (IF) and a digital cascade-of-integrators, feedback form (CIFB) delta sigma modulator. The latter is to push the quantized noise to the high frequency and quantizes the output to 1-bit. The class D audio amplifier employs an improved half bridge circuit. The improved class D amplifier can achieve similar total harmonic distortion as the H-bridge circuit has. An off-chip active low pass filter is used to filter the out-of-band noise. The entire system drive a headset or an active speaker, providing a CD quality audio signal. The chip is realized using TSMC 0.18-µm CMOS process. The total area including I/O pads is approximately 1.373mm2. The power consumption is 3.51mW and the THD is -85dB when a 1K Hz signal is applied.

[1] Richard Schreier, Gabor C. Temes, Understanding Delta-Sigma Data Converters. NY : Wiley-Interscience, 2005
[2] Steven R. Norsworthy, Richard Schreier, Gabor C. Temes, Delta-Sigma Data Converters Theory, Design, and Simulation. NY : Wiley-Interscience, 1996.
[3] Eric Gaalaas, “Class D audio amplifier: what, why, and How,” Analog Dialogue, vo1. 40, no. 2, pp.6 – 12, 2006
[4] Jinho Noh, Dongjun Lee, Jun-Gi Jo, and Ghamgsik Yoo “A class-D Amplifier with PWM digital input for digital hearing aid” IEEE journal of solid state circuit, vol. 48, pp.465 – 472, 2013
[5] Shumeng Luo and Dongmei Li “A sixth order PWM Modulator for Digital input class-D Audio Amplifier,” ICCIS, Fifth International conference on International Conference on Computer and Information Sciences (ICCIS), pp.1253 – 1256, 2013
[6] Kyoungsik Kang, Jeongjjin Roh, Youngkil Choi, Hyungdong Roh, Hyunsuk Nam, and Songjun Lee “Class D Audio amplifier using 1-bit forth-order Delta-sigma modulation,” IEEE, Transactions on circuits and system II: Express Briefs, vol 55, pp.728~732, 2008
[7] Analog Devices, SSM2537 “PDM Digital Input, Mono 2.7W Class-D Amplifier”
[8] Maxim Integrated , MAX98356 “PDM input Class D audio Power Amplifier”
[9] Delta-Sigma toolbox (http://www.math-works.com/matlabcentral/fileexchange)
[10] G. A. S. Machado, N. C. Battersby, and C. Tomazou,“On the Development of Analogue Sampled-Data Signal Processing,”in Proc. Analog Integrated Circuits and Signal Processing, vol. 12, no. 3, Apr. 1997, pp. 179-199.
[11] D. A. Johns and K. Martin, Analog Integrated Circuit Design, NY : John Wiley & Sons, Inc., 1997.
[12] 黃濬杰，「低功耗之二階強健式多級三角積分類比數位轉換器｣ ，國立台灣科技大學電機工程學系碩士論文，中華名國一百零二年一月。
[13] 王勝賢，「應用於音頻數位/類比轉換器之多位元三角積分調變系統設計與實現｣，國立台灣大學電信工程研究所碩士論文，中華民國九十五年六月。
[14] 杜宜融，「單電感雙輸出降壓轉換器與D類放大器設計｣，國立台北科技大學電腦與通訊研究所碩士論文，中華民國九十五年六
[15] B. Razavi, Design of Analog CMOS Integrated Circuit. US, McGraw-Hill, 2001.
[16] P. P. Vadiyanathan, and Troung O. Nguyen“A TRICK for the Design of FIR Half- Band Filter,”IEEE Transactions on Circuits and Systems, vol34, pp.297 – 300, 1987.
 
[17] Red pitaya (http://redpitaya.readthedocs.io/en/latest/)
[18] Martin Kinyua, Ruopeng Wang, and Eric Soenen“Integrated 105 dB SNR, 0.0031% THD+N Class-D Audio Amplifier With Global Feedback and Digital Control in 55 nm CMOS” IEEE Journal of Solid-State Circuits, vol50, pp.1764 – 1771, 2015.
[19] Chien-Hung Kuo, and Sheng-Chi Lin“A delta-sigma modulator-based class-D amplifier”IEEE 5th Global Conference on Consumer Electronics, pp.1 – 2, 2016.
[20] Chih-Min Chang, and Jieh-Tsorng Wu“A 95-dBA DR Digital Audio Class-D Amplifier Using a Calibrated Digital-to-Pulse Converter” IEEE Transactions on Circuits and Systems I: Regular Papers, vol64, pp.1106 – 1107, 2017.
[21] Texas Instruments, TAS2505 “Digital input class-D speaker amplifier with audio processing and mono headphone amplifier”