Erratum: Improved common-mode feedback circuit suitable for operational transconductance amplifiers with tuning

1991 ◽  
Vol 27 (9) ◽  
pp. 787
Author(s):  
P. Wu ◽  
R. Schaumann
Keyword(s):  
Feedback Circuit ◽  
Common Mode ◽  
Operational Transconductance Amplifiers ◽  
Transconductance Amplifiers

scholarly journals Design Trade-Offs in Common-Mode Feedback Implementations for Highly Linear Three-Stage Operational Transconductance Amplifiers

Electronics ◽  
2021 ◽  
Vol 10 (9) ◽  
pp. 991
Author(s):  
Joseph Riad ◽  
Sergio Soto-Aguilar ◽  
Johan J. Estrada-López ◽  
Oscar Moreira-Tamayo ◽  
Edgar Sánchez-Sinencio
Keyword(s):  
Cmos Technology ◽  
Common Mode ◽  
Operational Transconductance Amplifiers ◽  
Fully Differential ◽  
Trade Offs ◽  
Active Rc Filter ◽  
Transconductance Amplifiers ◽  
Two Stages ◽  
The Impact

Fully differential amplifiers require the use of common-mode feedback (CMFB) circuits to properly set the amplifier’s operating point. Due to scaling trends in CMOS technology, modern amplifiers increasingly rely on cascading more than two stages to achieve sufficient gain. With multiple gain stages, different topologies for implementing CMFB are possible, whether using a single CMFB loop or multiple ones. However, the impact on performance of each CMFB approach has seldom been studied in the literature. The aim of this work is to guide the choice of the CMFB implementation topology evaluating performance in terms of stability, linearity, noise and common-mode rejection. We present a detailed theoretical analysis, comparing the relative performance of two CMFB configurations for 3-stage OTA topologies in an implementation-agnostic manner. Our analysis is then corroborated through a case study with full simulation results comparing the two topologies at the transistor level and confirming the theoretical intuition. An active-RC filter is used as an example of a high-linearity OTA application, highlighting a 6 dB improvement in P1dB in the multi-loop implementation with respect to the single-loop case.

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