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Different Approach In Design And Analysis Of An Instrumentation Amplifier

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1996 Annual Conference


Washington, District of Columbia

Publication Date

June 23, 1996

Start Date

June 23, 1996

End Date

June 26, 1996



Page Count


Page Numbers

1.165.1 - 1.165.5



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Paper Authors

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Bahman Motlagh

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Walter Buchanan

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Alireza Rahrooh

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NOTE: The first page of text has been automatically extracted and included below in lieu of an abstract

. Session 3547

Different Approach in Design And Analysis of an Instrumentation Amplifier

Alireza Rahrooh, Walter W. Buchanan, Bahman Motlagh University of Central Florida/Middle Tennessee State University/University of Central Florida


This paper presents a diilerent instrumentation amplifier design to minimize the magnitude and phase errors of conventional instrumentation amplifier using single-pole model of the operational amplifler. l’his analytical approach ensures maximum flat magnitude and phase responses over an extended frequency range. Simulation results are given to support the proposed technique.

Design And Analysis Using Single-Pole Model

There are numerous applications in which a diiRerential signal needs to be amplified. These include low- level bridge measurements, balanced microphone lines, communication equipment, thermocouple amplifiers, data acquisition, and more 1. The immediate answer to these applications is the WXerential operational amplifier configuration. There are limitations to dii3erential amplifiers, tiortunately. It is practically impossible to achieve matched high-impedance inputs while maintaining high gain and satisfactory offset and noise performance. For that matter, the input impedances are not iso~ed; indeed, the impedance of one input may very well be a fimction of the signal present on the other input . Thus, this is an unacceptable situation when a precision amplifier is needed, particularly if’the source impedance is not very low.

An instrumentation amplifier (1-Anrp) overcomes these problems. Instrumentation amplifiers offer very high impedance, isolated inputs along with high gain, and excellent common-mode rejection performance. Instrumentation amplifiers can be fashioned from separate Op-Amps. They are also available on a single IC for highest performance. The common structure of an I-Amp is given in figure 1. The fist-order model of operational amplifier open-loop gain is given by

z%) (!.). CD. A(jo) = = — (1) jm+o. ja+03C

where &is the open-loop dc gain, OC is the corner frequency, and co. is the unity gain bandwidth of the operational amplifier. An approximated model at higher frequency can be written as


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Motlagh, B., & Buchanan, W., & Rahrooh, A. (1996, June), Different Approach In Design And Analysis Of An Instrumentation Amplifier Paper presented at 1996 Annual Conference, Washington, District of Columbia. 10.18260/1-2--5993

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