Probing Techniques for GaN Power Electronics: How to Obtain 400+ MHz Voltage and Current Measurement Bandwidths without Compromising PCB Layout

Printed circuit board (PCB) layout critically influences the performance of GaN power electronic circuits, in terms of switching speed, overshoots, ringing, and generated EMI. Typically, low-impedance layout of gate-drive loops and switching cells is vital for performance. This paper briefly examines the circuit impedances required for adequate performance, and the bandwidth needed for measurement of switching waveforms. It is shown that many high-bandwidth voltage and current probing methods are not compatible with the circuit-layout requirements. The paper then presents PCB layout and probing techniques, including an updated version of the “Infinity” current sensor, that achieve both high-fidelity, wide-bandwidth (400+ MHz) voltage and current measurements, and clean, efficient switching.