An operational transconductance amplifier (OTA) is a major building block and consumes most of the power in switched-capacitor (SC) circuits, but it is difficult to design low-voltage OTAs in scaled CMOS technologies. Instead of using an OTA, this paper proposes an inverter-based SC circuit and its application to low-voltage, low-power delta-sigma $(\Delta \Sigma)$ modulators. Detailed analysis and design optimizations are also provided. Three inverter-based $\Delta \Sigma$ modulators are implemented for an implantable pacemaker, a CMOS image sensor, and an audio codec. The modulator-I for an implantable pacemaker achieves 65-dB peak-SNDR for 120-Hz bandwidth consuming 0.73 $\mu$ W with 1.5 V supply. The modulator-II for a CMOS image sensor implemented with 320-channel parallel ADC architecture achieves 63-dB peak-SNDR for 8-kHz bandwidth consuming 5.6$\ \mu$W for each channel with 1.2-V supply. The modulator-III for an audio codec achieves 81-dB peak-SNDR with 20-kHz bandwidth consuming 36 $\mu$W with 0.7-V supply. The prototype $\Delta \Sigma$ modulators achieved high power efficiency maintaining sufficient performances for practical applications.
Bibliographical noteFunding Information:
Manuscript received January 08, 2008; revised August 28, 2008. Current version published January 27, 2009. This work was supported by Samsung Electronics Co. Ltd. The authors are with the Department of Electrical and Electronic Engineering, Yonsei University, Seoul 120-749, Korea (e-mail: firstname.lastname@example.org). Digital Object Identifier 10.1109/JSSC.2008.2010973
All Science Journal Classification (ASJC) codes
- Electrical and Electronic Engineering