A High Slew-Rate Enhancement Class-AB Operational Transconductance Amplifier (OTA) for Switched-Capacitor (SC) Applications

Abstract

This article presents a class-AB operational transconductance amplifier (OTA) with a high slew rate. The proposed class-AB OTA is applied with a slew-rate enhancement technique using an extremely low quiescent current. The additional current-reference common-mode feedback loop resolves the susceptibility to process, voltage, and temperature fluctuations resulting from slew-rate enhancement transistors. The proposed class-AB OTA is most widely used in block design, including, a switched-capacitor circuit, analog-to-digital converter, digital-to-analog converter, low-dropout regulator, and switched-capacitor DC-DC converters. In this study, performance was validated by applying the proposed class-AB OTA to a switched-capacitor delta-sigma modulator which requires high performance and high precision. The circuit was designed and simulated using a 0.18-μm complementary metal-oxide semiconductor process.

Keywords

• Operational transconductance amplifier
• slew-rate
• class-AB
• delta-sigma modulator
• feedforward architecture
• switched-capacitor