A Compact GaNFET-Based Power Amplifier for ASIC-Based Miniature NMR Spectrometers

This paper describes a highly-efficient and compact GaNFET-based power amplifier for use in miniaturized low-field nuclear magnetic resonance (NMR) spectrometers and magnetic resonance imaging (MRI) scanners based on CMOS application-specific integrated circuit (ASICs). The amplifier utilizes a H-bridge topology with bootstrap driver and can work at frequencies up to several MHz. It also includes a GaNFET-based Q-switch to damp the coil after each RF pulse. Tests with a tuned probe at 2 MHz show > 90% efficiency while delivering ~350 W of power to the coil, and a ring-down time of ~4 μs.