Estimation of Rise Time of Discharge Current for Air Discharge of ESD-Gun with Low Charge Voltages

With a 12-GHz digital oscilloscope, we measured discharge current waveforms for air discharges of an ESD-gun less than 1 kV onto a 50-Omega SMA connector. To grasp real rise time of the observed waveforms, we reconstructed input current waveforms from complex frequency responses of the first and second order for the vertical amplifier of oscilloscopes, and estimated the rise time concerning them. As a result, we found that the frequency response measured for the oscilloscope agrees well with that of second order, which gives a minimum rise time of 27 ps at 300V.