Amplifier gets ‘extreme’ makeover

Electrical engineering researchers at the University of Arkansas have designed a fully differential amplifier that can operate in a space environment without requiring protection from extreme temperatures and radiation.

Said to be capable of achieving a large differential gain consistently and with stability at temperatures between 125oC and -18oC, the amplifier has been designed to achieve power and footprint savings when integrated in space applications. The research was presented at the 2009 IEEE Aerospace Conference.

“This and several other designs focus on wide-temperature operational characteristics of sensor-based, signal-processing circuits,” said Alan Mantooth, professor of electrical engineering and holder of the 21 Century Endowed Chair in Mixed-Signal IC Design and CAD. “But our device is the first fully differential amplifier circuit designed specifically for extreme temperatures, including temperatures in the cryogenic region. Some of our designs have been tested as fully operational down to 2 Kelvin, or -271oC.”

Under Mantooth's direction, electrical engineering graduate students Kimberly Cornett and Ivonne Escorcia and post-doctorate fellow Guoyuan Fu developed a device with common-mode feedback circuits on both the input and output stages to facilitate fine-tuning and achieve a higher quality output signal.

Commenting on the amplifier design, which has been made in a commercially available semiconductor process, Cornett noted: “Although the design of the dual common-mode feedback in our circuitry is not especially unique, we were able to determine through simulation across the temperature range that using feedback around both stages of the amplifier provided better control of the output common-mode voltage.” However, she explained: “The research work on this amplifier is part of a larger project to develop extreme environment electronics in commercially available SiGe as a part of the NASA Exploration Technology Development Program (ETDP). Other members of the project include the Georgia Institute of Technology (team lead), University of Tennessee, Auburn University, Vanderbilt University, University of Maryland, NASA's Jet Propulsion Laboratory, Boeing, BAE Systems, IBM and Lynguent. As a group we have developed a library of circuits that operate in this wide temperature range, including a full digital gate library, digital to analog converters, analog to digital converters, several amplifiers, high voltage transistors, flying capacitor switch circuits, and several other building blocks. The goal is to provide integrated solutions that can replace entire systems that previously required 'warm box' protection from both wide temperatures and radiation exposure.”

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