Analysis and design of highly linear triode‐mode based OTA and its application to a wide tunable Gm‐C filter

• Published in: International journal of circuit theory and applications 2017-09, Vol.45 (9), p.1218-1230
• Main Authors: Rezaei, Farzan, Carvajal, Ramón G.
• Format: Article
• Language: English
• Subjects: Cascode transistors; CMOS; Cut-off; Design analysis; Feedback circuits; Gm‐C filter; harmonic distortions; Linearity; Operational amplifiers; OTA; Power consumption; Semiconductor devices; Simulation; Transconductance; Transistors; triode‐mode transistor; tunable; Tuning
• ISSN: 0098-9886; 1097-007X
• DOI: 10.1002/cta.2372

Summary In this paper, a new highly linear operational transconductance amplifier (OTA) based on triode‐mode input transistors is introduced. An analysis based on theoretical relations and simulation results is presented that aims to obtain the best operating points of triode‐mode and cascode transistors to achieve the highest linearity. The proposed analysis is utilized to design a linear pseudo‐differential OTA, benefiting a linear common mode feedforward and an appropriate common mode feedback circuit. The common mode feedforward circuit is also regulated in the same manner as main the transconductor to stabilize the output common mode voltage during tuning action and achieve higher common mode rejection ratio. Proposed OTA is used to implement a tunable low‐power linear Gm‐C filter. The cutoff frequency of the filter is tunable from 2.7 to 44 MHz while its power consumption changes from 3.5 to 8.5 mW in the entire tuning range. By applying input voltages up to 1.1 Vp‐p, the filter's IM3 remains less than −48 dB for various cutoff frequencies. The proposed OTA and filter are simulated in 0.18‐μm CMOS technology with Hspice simulator. Copyright © 2017 John Wiley & Sons, Ltd. In this paper, a new highly linear operational transconductance amplifier based on triode‐mode input transistors is introduced. An analysis is presented that aims to obtain the best operating points of triode‐mode and cascode transistors to achieve the highest linearity. The proposed operational transconductance amplifier is used to implement a tunable low‐power linear Gm‐C filter. The cutoff frequency of filter is tunable from 2.7 to 44 MHz while its power consumption changes from 3.5 to 8.5 mW in the entire tuning range.