Design methodology for common-mode stability of OTA-based gyrators

This paper presents a design methodology for common-mode (CM) stability of operational transconductance amplifier (OTA)-based gyrators. The topology of gm − C active inductors is briefly reviewed. Subsequently, a comprehensive mathematical analysis on the CM stability of OTA-based gyrators is presented. Sufficient requirements for the gyrator’s CM stability, that easily can be considered during the design process of common-mode feedback (CMFB) amplifiers, are defined. Based on these stability requirements, a design methodology and a design procedure are proposed. Finally, in order to validate the proposed procedure, a resonator with 20 MHz resonance frequency and a quality factor of 20 is fabricated with UMC 180-nm CMOS technology and its CM stability is examined. Keywords—Common-mode stability, gm − C filters, gyrator, operational transconductance amplifier (OTA), resonator.