Analysis of high-frequency electromagnetic ringing phenomenon under GaN-FET inverter excitation

In this study, the ringing phenomenon of gallium nitride-field effect transistor (GaN-FET) and silicon-insulated gate bipolar transistor (Si-IGBT) inverter excitations in a ring sample was thoroughly measured and analyzed by using a high-quality oscilloscope with a very high sampling rate of 5 giga-samples per second (GS/s). Owing to the rapid switching of the GaN-FET power devices in several nanoseconds and the ringing frequencies in the MHz range, the use of the high sampling rate of 5 GS/s is necessary and useful for accurate measurement. The experimental findings and analysis reveal the following three key points: (i) there are two possible types of high-frequency resonance phenomena, that is, the first one caused by semiconductor devices and circuits and the other generated by the resonance with loads in use. (ii) The ringing phenomenon because of the resonance under the load is considered to be due to the rising time of pulses that are caused by the rapid switching of the semiconductor devices. (iii) The ability to measure and the two types of ringing phenomena depends on the intensity of the white noise of the measuring instrument