Title :
A low-noise CMOS preamplifier operating at 4.2 K
Author :
Kleine, U. ; Bieger, J. ; Seifert, H.
Author_Institution :
Corp. Res. & Dev., Siemens AG, Munich, Germany
fDate :
8/1/1994 12:00:00 AM
Abstract :
A low-noise CMOS readout preamplifier operating at liquid helium temperatures is described, In conjunction with magnetic field sensors applying SQUIDs (superconducting quantum interference devices) the preamplifier can be used to measure biomagnetic fields of human brain and heart noninvasively. The input of the folded cascode amplifier can be attached directly to a low impedance SQUID output. This way the commonly used discrete LC tank resonator circuit for impedance matching can be omitted. An equivalent noise voltage density of 0.3 nV/√Hz at 500 kHz has been measured. Despite the occurrence of the kink effect and other abnormalities in MOS transistor characteristics at 4.2 K, during the tests no abnormal operation has been observed. Such a preamplifier circuit is essential in simplifying the expensive shielding currently used in biomagnetic diagnosis systems
Keywords :
CMOS integrated circuits; SQUIDs; biomagnetism; biomedical electronics; biomedical measurement; cryogenics; electric sensing devices; impedance matching; linear integrated circuits; magnetic field measurement; preamplifiers; 4.2 K; MOS transistor characteristics; SQUID; biomagnetic fields; folded cascode amplifier; heart; human brain; kink effect; liquid He temperatures; low-noise CMOS preamplifier; magnetic field sensors; noninvasive measurement; readout preamp; superconducting quantum interference devices; Biomagnetics; Biosensors; Circuits; Helium; Magnetic field measurement; Magnetic liquids; Magnetic sensors; Preamplifiers; SQUIDs; Temperature sensors;
Journal_Title :
Solid-State Circuits, IEEE Journal of
