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A novel OTA compensation approach suitable for CT‐ΔΣ modulators
Author(s) -
Hasanzadeh Mohammad Reza,
Abrishamifar Adib
Publication year - 2018
Publication title -
international journal of circuit theory and applications
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.364
H-Index - 52
eISSN - 1097-007X
pISSN - 0098-9886
DOI - 10.1002/cta.2516
Subject(s) - frequency compensation , delta sigma modulation , electronic engineering , operational transconductance amplifier , compensation (psychology) , linearity , cmos , amplifier , phase margin , transconductance , bandwidth (computing) , operational amplifier , distortion (music) , computer science , engineering , electrical engineering , telecommunications , transistor , voltage , psychology , psychoanalysis
Summary In this paper, a frequency‐compensation approach to improve the phase margin of CMOS operational‐transconductance‐amplifiers (OTAs) is discussed particularly for use in continuous‐time delta‐sigma modulators (CT‐ΔΣMs). The proposed method benefits a simple RC compensation network to provide one‐dominant pole amplifier while its linearity is improved, too. Analytical and mathematical calculations are developed at macromodel and circuit level to prove the advantage of proposed method to conventional compensation topologies. Using TSMC‐0.18 μm CMOS process, the behaviors of some OTAs are analyzed in a case study, 20‐MHz bandwidth third‐order CT‐ΔΣ modulator. Simulations show that using proposed OTA, significant improvement is achieved in the signal‐to‐noise‐and‐distortion‐ratio compared with the same modulator that employs other types of frequency compensation for its amplifiers.