Avalanche Transistor-Based Nanosecond Pulse Generator

There is an increasing interest in fast rise time high voltage (HV) pulse generators employed in spark gap triggering, X-ray generation, microwave antenna, pulsed laser, plasma research, biological effects on cells and industrial applications among others. Traditionally, Marx generators are employed for these applications with gas breakdown spark gaps. However, the Marx generators are of a higher rise time, due to parasitic inductances and capacitances of the spark gaps and electrical connections. This in turn increases the volume of the system. In order to reduce parasitic inductance and capacitance, a compact and modular design is proposed in this paper. This output voltage of the pulse generator was used to trigger a gaseous spark gap of 5 kV operating voltage. LTspice simulation studies were performed on pulse generator circuit to generate 10 kV with 6 ns peak time. Two-stage Marx circuit-based pulse generator is designed using avalanche transistors (AT) and experimentally validated. Each stage consists of 13 numbers ATs in series. Disk ceramic capacitors charge up to supply voltage through the isolating resistors. To achieve fast rise time, the loop inductance was minimized through assembly of these components in strip-line geometry over a two-layer printed circuit board (PCB). Output peak voltage of 10 kV, rise time of 3.5 and 0.4 ns jitter in rise time were measured during multiple shots on single AT Marx circuit.