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Variability in AC amplifier distortions: Estimation and correction

Published online by Cambridge University Press:  20 August 2002

C.A. JOYCE ,
I.F. GORODNITSKY ,
W.A. TEDER-SÄLEJÄRVI ,
J.W. KING  and
M. KUTAS
C.A. JOYCE
Affiliation:
Department of Computer Science, University of California, San Diego, California, USA
I.F. GORODNITSKY
Affiliation:
Department of Cognitive Science, University of California, San Diego, California, USA
W.A. TEDER-SÄLEJÄRVI
Affiliation:
Department of Neurosciences, University of California, San Diego, California, USA
J.W. KING
Affiliation:
Department of Psychology, University of Missouri, Columbia, Missouri, USA
M. KUTAS
Affiliation:
Department of Cognitive Science, University of California, San Diego, California, USA Department of Neurosciences, University of California, San Diego, California, USA
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Abstract

AC amplifiers can introduce significant distortions into the low frequency and DC components of recorded electrophysiological data such as event-related potentials (ERPs). Methods for correcting such distortions (i.e., estimating the waveform of the original data) after the data have been amplified and recorded rely on an accurate estimate of the amplifier's time constant (TC). We show that the filter characteristics of AC amplifiers in at least some commercially available ERP recording instruments may vary considerably across individual channels, even when each houses an identical AC amplifier circuit. Clearly, distortion correction methods must take this variability into account. We propose an empirical means of estimating the correct TC value. This approach yields more accurate correction than those based on TCs calculated analytically.

Keywords

Time constantAC-amplifier fluctuationsDC recovery
Type
Research Article
Information
Psychophysiology , Volume 39 , Issue 5 , September 2002 , pp. 633 - 640
Copyright
© 2002 Society for Psychophysiological Research

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