Very Low 1/f Noise and Radiation-Hardened CMOS Preamplifier for High-Sensitivity Search Coil Magnetometers

A 4 nV/root Hz at 10 Hz preamplifier with a 12-mW power consumption in complimentary metal-oxide-semiconductor 0.35 mu m technology has been developed to go one step further in the integration of the preamplifier of a search coil magnetometer. The present application-specific integrated circuit (ASIC) preamplifier, combined with a 10-cm length, 12-mm diameter, and 15 000 turns search coil sensor demonstrates a noise equivalent magnetic induction as low as 2 pT/root(Hz) at 10 Hz and 14 fT/root(Hz) at 4 kHz. The measured current noise is only 46 f A/root Hz. AC magnetometers (from 100 mHz to a few kHz) based on search coil sensors are used for space plasma physics investigations because of their excellent robustness and very high sensitivity. The present ASIC preamplifier offers a way to considerably save weight, volume, and power. This paper will focus on the design of the ASIC, driven by the following criteria: low thermal and 1/f noise, radiation hardness for space purpose, and power consumption.