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

Volume

29

Issue

8

fYear

1994

fDate

8/1/1994 12:00:00 AM

Firstpage

921

Lastpage

926

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;

fLanguage

English

Journal_Title

Solid-State Circuits, IEEE Journal of

Publisher

ieee

ISSN

0018-9200

Type

jour

DOI

10.1109/4.297696

Filename

297696