Three Separate Nanosecond Rise Time Pulse Generators Using Npn Transistors

A five-stage Marx bank was constructed using surface-mount capacitors and NPN transistors . An output pulse rise time of two nanoseconds with a pulse duration of five nanoseconds at a continuous repetition rate of 40 kHz and a worst case peak power of 6.5 kW was achieved. The two-nanosecond rise time for the Marx bank was accomplished by biasing the transistors in the avalanche mode. The emphasis in the design was on miniatarization and reliability since the unit was to be submerged down a well hole to a depth of 500 meters. To increase the output power for another application, three solid-state Marx banks were connected in parallel. Synchronization for the parallel firings of the Marx banks was the critical design issue. A third application required that two of the avalanche circuits be triggered at precisely-controlled time differences.