Study of capacitance nonlinearity in nano-scale multi-stage MOSFET-only sigma-delta modulators

Aminzadeh, Hamed

doi:10.1016/j.aeue.2018.01.003

Cited by 10 publications

(4 citation statements)

References 22 publications

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“…If not satisfied, we should either increase R k or decrease R Ak for the condition to be met. Reducing R Ak , however, enlarges the required C Ak according to the first condition in (6). The following design expressions can be therefore considered as the general rules for R Ak and C Ak , given that Z k should be unchanged for the frequency range between 0.1 × GBW and 10 × GBW:…”

Section: The Concept Of Gia In Generalmentioning

confidence: 99%

“…Multistage operational transconductance amplifier (OTA) in closed-loop configuration is one of the basic building blocks used extensively to buffer and amplify the voltage and current signals generated by a variety of integrated circuits (ICs), from discrete-time switched-capacitor analog-to-digital and digital-to-analog converters to continuous-time filters, low-dropout regulators (LDOs), audio amplifiers and active-matrix liquid crystal displays (LCDs), micro-electromechanical systems (MEMS), and line drivers. [1][2][3][4][5][6][7][8][9][10] Many applications falling into these categories favor an amplifier that can drive a naturally variable load capacitor (C L ) since this parameter experiences remarkable excursions during the start-up and normal operation of the OTA. In some applications, the change of C L is not significant, yet the design should be robust to C L variations.…”

Section: Introductionmentioning

confidence: 99%

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Global impedance attenuation network for multistage OTAs driving a broad range of load capacitor

Aminzadeh

Valinezhad

Grasso

2020

Circuit Theory & Apps

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Summary Advanced multistage amplifiers suffer from load‐dependent stability issues, which limit the load capacitor range they can drive. In this work, the concept of global impedance attenuation (GIA) network is introduced to improve an amplifier's stability in the presence of significant load capacitor variations. Composed of multiple parallel resistor‐capacitor (RC) branches, the equivalent high‐frequency output impedance of gain stages is shaped by the GIA network such that a desired frequency spectrum is obtained over a wide range of load capacitor. The parasitic poles at the output of the gain stages are nullified by the proposed network, thereby simplifying the amplifier's transfer function and reducing the minimum load capacitor it can drive. The idea is applied to design a three‐stage operational transconductance amplifier (OTA) with cascode global impedance attenuation (CGIA). Small‐signal analysis shows that the OTA is stable regardless of the load capacitor, and it can drive very small to ultra‐large load capacitors. This feature is verified by the post‐layout simulations of a CGIA amplifier in 0.18‐μm complementary metal‐oxide semiconductor (CMOS) process. The core occupies a die area of 0.0053 mm2 while consuming a static current of 10.97 μA from 1.8‐V voltage supply. The unity‐feedback configuration is unconditionally stable for any load capacitor higher than 10 pF. To the best of our knowledge, this corresponds to the widest range of load capacitance reported for prior‐art three‐stage amplifiers.

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Section: The Concept Of Gia In Generalmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Global impedance attenuation network for multistage OTAs driving a broad range of load capacitor

Aminzadeh

Valinezhad

Grasso

2020

Circuit Theory & Apps

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“…Within this framework, one of the commonly used applications of the high-gain operational transconductance amplifiers (OTAs) was to provide a reliable amplified signal for the capacitive loads (CLs) reaching tens of nanofarad. Some principal blocks that call for such specifications are active-matrix liquid crystal displays (LCDs), low-dropout regulators (LDOs), active filters, analog-to-digital converters, and line drivers [6], [7], [8], [9], [10], [11].…”

Section: Introductionmentioning

confidence: 99%

Hybrid Cascode Frequency Compensation for Four-Stage OTAs Driving a Wide Range of C _L

Aminzadeh,

Ballo,

Grasso

et al. 2023

IEEE Trans. VLSI Syst.

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Feedback amplifiers consisting of multiple gain stages are used to establish highly accurate buffered/amplified signals that can drive a wide range of capacitive load (CL). This article models, analyzes, and presents the measurement results of a high-gain four-stage operational transconductance amplifier (OTA) that is able to handle a wide range of CL up to infinity. In addition to local compensation capacitors and nulling resistors in the intermediate stages, two high-speed feedback loops made by parallel Miller capacitors and current buffers provide Miller compensation and the consequent pole-splitting in the lower CL range. The dominant pole is made dependent on the CL for the higher CL range, enabling the maintenance of the stability conditions up to infinite CL. The proposed amplifier was integrated into a 65-nm CMOS technology, consuming 140-µA static current under a 1.2-V supply and an active area of 0.0086 mm 2 . A dc gain greater than 100 dB was also perceived with a unity-gain frequency (UGF) of 4.09, 2.01, and 0.27 MHz for 4.7, 10, and 100-nF load capacitors, respectively. The average slew rate (SR) is 0.59 V/µs, when the OTA is formed as a buffer targeting the CLs higher than 4.7-nF.

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“…Integrated digital-to-analog and analog-to-digital data converters (Aminzadeh, 2018c), low-dropout voltage regulators (LDOs) and continuousand discrete-time filters (Aminzadeh, 2018b) all need highspeed yet high gain operational amplifiers which can operate reliably after applying feedback. Low-power amplifiers with sufficient accuracy can be implemented using the long-channel MOS devices found in micro-scale CMOS technologies, where the supply voltage is high enough to satisfy the required dynamic range.…”

Section: Introductionmentioning

confidence: 99%

A reliable model for the compensation loop of multistage amplifiers at high frequency

Aminzadeh

2019

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Purpose Multistage amplifiers require a reliable frequency compensation solution to remain stable in a closed-loop configuration. A frequency compensation scheme creates an inner negative feedback loop amongst different amplifying stages and shapes the frequency response such that an unconditionally stable single-pole amplifier results for closed-loop operation. The frequency compensation loop is thus responsible for the placement of the poles and zeros and the final stability of multistage amplifiers. An amplifier incorporating a sophisticated frequency compensation network cannot be, however, analyzed in the presence of a complex ac feedback loop. The purpose of this study is to provide a reliable model for the compensation loop of multistage amplifiers at the higher frequencies. Design/methodology/approach In this paper, the major part of the amplifier, including a two-port network comprising the compensation network, is characterized using a reliable feedback model. Findings The model integrates all the frequency-dependent components of the frequency compensation network, and it can evaluate the nondominant real or complex poles of an amplifier. Originality/value The reliability of the proposed model is verified through analysis of the frequency response of the amplifiers and by comparing the analytic results with the simulation results in standard CMOS process.

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Study of capacitance nonlinearity in nano-scale multi-stage MOSFET-only sigma-delta modulators

Cited by 10 publications

References 22 publications

Global impedance attenuation network for multistage OTAs driving a broad range of load capacitor

Global impedance attenuation network for multistage OTAs driving a broad range of load capacitor

Hybrid Cascode Frequency Compensation for Four-Stage OTAs Driving a Wide Range of C _L

A reliable model for the compensation loop of multistage amplifiers at high frequency

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Study of capacitance nonlinearity in nano-scale multi-stage MOSFET-only sigma-delta modulators

Cited by 10 publications

References 22 publications

Global impedance attenuation network for multistage OTAs driving a broad range of load capacitor

Global impedance attenuation network for multistage OTAs driving a broad range of load capacitor

Hybrid Cascode Frequency Compensation for Four-Stage OTAs Driving a Wide Range of C L

A reliable model for the compensation loop of multistage amplifiers at high frequency

Contact Info

Product

Resources

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Hybrid Cascode Frequency Compensation for Four-Stage OTAs Driving a Wide Range of C _L