![]() Since a very low noise factor is essential for MRI preamplifiers, noise contributions from passive components in the MRI preamplifier have to be considered during the stabilization process. Different approaches to improve stability were used during this derivation. ![]() In this article, a coil-loading-insensitive preamplifier for MRI is presented, derived from an unstable preamplifier. Therefore preamplifiers which stability is not sensitive to coil loading are desirable. Under various loading conditions of the corresponding receiver coils, preamplifiers see different source impedance at their input and may become unstable. In MRI (magnetic resonance imaging), preamplifiers are needed to amplify signals obtained from MRI receiver coils. Gruschke, Oliver Hennig, Jürgen Zaitsev, Maxim ![]() With fewer components, these matching networks showed lower noise factors, while similar preamplifier-decoupling performance was found for all three methods.ĭesign of a 3T preamplifier which stability is insensitive to coil loadingĬao, Xueming Fischer, Elmar Korvink, Jan G. Phase shifting networks between coils and preamplifiers are not necessary in our matching methods. Decoupling and noise-matching performance were compared between these three configurations. These matching methods and, for comparison, the conventional matching method were implemented with custom-made preamplifiers and coils. Furthermore, coil matching networks and preamplifier input matching networks were combined, meaning the coil loop can be matched to the transistor in the preamplifier directly. Instead of compensating the reactance of the input impedance of preamplifiers, in our method, the reactance was used to resonate with the coil matching networks and thus to decouple the coils. In this paper, direct matching methods for coils and preamplifiers in receiver arrays are presented. The Guralp GS13 Preamplifiers are being evaluated for potential use in the International Monitoring System (IMS) of the Comprehensive Nuclear Test-Ban-Treaty Organization (CTBTO).ĭirect matching methods for coils and preamplifiers in MRIĬao, Xueming Fischer, Elmar Hennig, Jürgen Zaitsev, Maxim The purpose of the preamplifier evaluation was to measure the performance characteristics in such areas as power consumption, input impedance, sensitivity, full scale, self-noise, dynamic range, system noise, response, passband, and timing. These preamplifiers are used to interface between Guralp digitizers and Geotech GS13 Seismometers. Sandia National Laboratories has tested and evaluated a new preamplifier, the Guralp Preamplifier for GS13, manufactured by Guralp.
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