Efficient Broadband Class AB Amplifier

• Main Authors: Silva-Martinez, Jose, Yan, Tanwei, Jiang, Junning, Shao, Jian
• Format: Conference Proceeding
• Language: English
• Subjects: Band-pass filters; Broadband Amplifiers; Cascode Amplifiers; Class AB Amplifiers; Logic gates; Low pass filters; Multi-stage Amplifiers; Power demand; Recycling; Recycling Amplifiers; Transconductance; Transistors
• ISSN: 1558-3899
• DOI: 10.1109/MWSCAS.2019.8885082

In this paper, feed-forward and class AB techniques are explored for the design of high-frequency Operational Transconductance Amplifiers (OTA) suitable for ADC architectures. The paper is focused on high gain broadband amplifiers; the first part of the paper revisited the recycling folded-cascode (RFC) architectures. These topologies are power efficient solutions but careful design is needed to avoid the presence of medium-frequency zero-pole pairs that may significantly increase residue amplifier settling time. The two stage class AB amplifier is revisited as well; the popular Monticelli's biasing circuit for class AB amplifiers is power efficient and result in high slew-rate solutions. An alternative class AB solution is proposed in this paper. The biasing of the class AB output stage employs a common-mode feedback, and results in a faster and more power efficient architecture; power consumption is around 75% that of the conventional class AB architecture and shows 3dB lower IM3 for the design of a state-variable 25MHz high-Q biquadratic filter.