Gigahertz, low-cost current shunt with retrofitting capability for characterization of fast-switching GaN devices

A low-cost current shunt based on a flexible polyimide printed circuit board (PCB) design is proposed in this article. With its low insertion inductance in the range of 300 pH and bandwidth in excess of 1 GHz, the design is well suited for characterization of very fast GaN devices. The thin layer-stack and bendability of the proposed sensor enables retrofitting into many existing designs that were not specifically prepared for current measurement. The ability to add and remove the sensors at different locations can significantly enhance investigations, e.g. when paralleling devices or during troubleshooting. Having the ability to retrofit a current sensor into low inductance commutation loops, even in fast GaN FET designs consisting solely of SMD devices, can be an alternative to designing specific PCBs just for switching characterization and can help to save time and resources in benchmarking. • Proposed low-cost current sensor based on standard polyimide PCBs is suitable for characterization of fast GaN FETs. • Bandwidth in excess of 1 GHz can be reached with suitable RC compensation. • Insertion inductance of proposed design is as low as 300 pH and does not require its own footprint. • Design enables high fidelity current sensing capability even on unprepared boards, helping to accelerate device benchmarking.