A MEMS-based precision operational amplifier

Two main difficulties for amplifiers that attempt to make precision DC measurements are the inherent low-frequency noise of the amplifier and the leakage current of the amplifier input stage. This thesis presents a novel fully integrated operational amplifier design that addresses both measurement limitations by using a fully differential mechanical transductor input stage, fabricated using SOI-MEMS technology. The input stage of the amplifier is a MEMS structure that provides a variable capacitance to transduce a low-frequency input voltage into a high-frequency AC current. This up-modulation of the input signal is exploited to reduce offsets and low-frequency noise, and the dielectric isolation of the MEMS structure provides high input impedance and low leakage currents. To function, the MEMS-based amplifier includes two co-dependent feedback loops. The 'drive loop' utilizes closed-loop control to vibrate the MEMS structure at its mechanical resonant frequency to produce a modulating capacitance. The 'sense loop' senses the up-modulated signal from the MEMS structure, and provides gain and demodulation to this signal. Global feedback around the sense loop allows for accurate measurement of the input voltage.

Department dc:contributor.department

Massachusetts Institute of Technology. Dept. of Electrical Engineering and Computer Science.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2004

Author dc:creator

• Paik, Song-Hee Cindy, 1980-

Advisor dc:contributor.advisor

• Kent H. Lundberg and Timothy A. Denison.

• Electrical Engineering and Computer Science.

Statement dc:rights

• M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/16682

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/16682