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Sensors 2018, 18(2), 393; https://doi.org/10.3390/s18020393

A Compact Operational Amplifier with Load-Insensitive Stability Compensation for High-Precision Transducer Interface

1
Department of Electrical Engineering, University of Southern California, Los Angeles, CA 90089, USA
2
Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
*
Author to whom correspondence should be addressed.
Received: 20 December 2017 / Revised: 14 January 2018 / Accepted: 24 January 2018 / Published: 29 January 2018
(This article belongs to the Section Physical Sensors)

Abstract

High-resolution electronic interface circuits for transducers with nonlinear capacitive impedance need an operational amplifier, which is stable for a wide range of load capacitance. Such operational amplifier in a conventional design requires a large area for compensation capacitors, increasing costs and limiting applications. In order to address this problem, we present a gain-boosted two-stage operational amplifier, whose frequency response compensation capacitor size is insensitive to the load capacitance and also orders of magnitude smaller compared to the conventional Miller-compensation capacitor that often dominates chip area. By exploiting pole-zero cancellation between a gain-boosting stage and the main amplifier stage, the compensation capacitor of the proposed operational amplifier becomes less dependent of load capacitance, so that it can also operate with a wide range of load capacitance. A prototype operational amplifier designed in 0.13- μ m complementary metal–oxide–semiconductor (CMOS) with a 400-fF compensation capacitor occupies 900- μ m 2 chip area and achieves 0.022–2.78-MHz unity gain bandwidth and over 65 phase margin with a load capacitance of 0.1–15 nF. The prototype amplifier consumes 7.6 μ W from a single 1.0-V supply. For a given compensation capacitor size and a chip area, the prototype design demonstrates the best reported performance trade-off on unity gain bandwidth, maximum stable load capacitance, and power consumption. View Full-Text
Keywords: analog integrated circuits; operational amplifiers; transducer interface circuit; Internet of Things (IoT) device analog integrated circuits; operational amplifiers; transducer interface circuit; Internet of Things (IoT) device
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Yu, Z.; Yang, X.; Chung, S. A Compact Operational Amplifier with Load-Insensitive Stability Compensation for High-Precision Transducer Interface. Sensors 2018, 18, 393.

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