Avalanche Transistor-Based Marx Generator Provides 1.15-kV/1-MHz Sub-Nanosecond Pulses Due to Triggering Acceleration

The high-voltage sub-nanosecond pulses with high repetition rate are widely used. The Marx-bank circuit (MBC) based on the avalanche bipolar junction transistor (ABJT) is an important and efficient choice to meet the above pulse requirements. However, in traditional MBC, the ABJTs triggered by voltage ramps at the first few stages have obvious reliability differences. The pulse repetition frequency (PRF) of MBC is commonly limited to the kHz level due to the failure of ABJT at the most vulnerable stage. By analyzing the switching transients of ABJT, this work shows that the device reliability is closely related to the slope of voltage ramp. The current paths of devices are experimentally observed and their formation processes and reliability differences are analyzed by simulation under different slope voltage ramp triggering conditions. The results show that the device triggered by slow voltage ramp is most vulnerable to damage due to its limited conductive width. Therefore, an improved MBC with triggering acceleration (MBC-TA) is proposed. The device reliability at the most failure-prone stage is improved by increasing the triggering speed. A 1
$\times$
15-stage MBC-TA is developed to verify the capability of high PRF and high reliability. It achieves an output amplitude of 1.15 kV, a rise time of 250 ps, a pulsewidth of 500 ps, and a PRF of 1 MHz. This investigation of device reliability and the improvement of MBC-TA provide a reference for the applications of MBCs based on ABJTs under high-frequency pulse conditions.