Active nuclear magnetic resonance probe: A new multidiciplinary approach toward highly sensitive biomolecoular spectroscopy

We present a fully integrated CMOS stacked detection inductor and front-end receiver for NMR applications. Instead of a planar CMOS NMR detection coil, we propose a multi-turn differential stacked inductor with hollowed core. Such a structure makes available the possibility of introducing minute analyte samples directly within the sensing coil with ensuing boost in NMR measurement sensitivity. Physical simulations of the hollowed inductor stack are used to verify the superiority of a differential coil topology. The front-end receiver contains LC pre-amplification, low-noise amplifier (LNA) and voltage buffer. Both the differential stacked detection inductor and front-end receiver are designed for 300 MHz NMR settings. The front-end receiver achieves an input referred noise of 780 pV/√Hz and voltage gain of 43 dB. The core of the LNA draws a DC current of 3.4-mA from a 1.6 V supply voltage. The chip is designed in a 0.13-μm CMOS technology and occupies an area of 1 mm × 2 mm.