Skip to Main Content
In order to considerably reduce circuit resources (mass, volume, and power) for the analog front ends of plasma wave measurement systems, a current-sensitive preamplifier for magnetic search coils (MSCs) is designed with standard 0.25- μm complementary metal-oxide-semiconductor (CMOS) technology. Since the input noise current determines the output noise levels around the resonant frequency of an MSC, a CMOS preamplifier operating with low noise current is suitable when combined with an MSC instead of using bipolar junction transistors. The current-sensitive CMOS preamplifier consists of a current amplifier for the detection of current flowing through the MSC and an equalizer for adjusting the transfer function. A prototype of the circuit structure was fabricated on a 1.9 × 3.3- mm2-silicon chip. The noise equivalent magnetic induction of the CMOS preamplifier combined with a 100-mm-long MSC is 3.5 pT/Hz1/2 at 10 Hz and 30 fT/Hz1/2 at 2 kHz with a power consumption of 4.6 mW for a 3.3-V supply. This paper is the first to examine a current-sensitive CMOS preamplifier for probing plasma waves.