Set-up and testing of a fast stacked-MOSFET switch

For experiments on electroporation of microalgae rectangular pulses with a pulse length of 10...20 ns and adjustable amplitude of up to 10 kV are required. The pulses are delivered by a cable pulse generator. A fast switch of stacked MOSFETs is replacing the formerly employed spark gap in order to enable a more precise control of switching moment and amplitude. The switch consists of separate stages, which have been designed for an operating voltage of 800 V across the switch and a maximum voltage of up to 1 kV. Each stage comprises two MOSFETs in parallel configuration for enhanced current capability, the driving circuitry, and local isolated power supply. In order to prevent over-voltage conditions to single stages due to delayed switching, a good synchronization of the stages is crucial. Hence, a fast rising trigger signal is employed, which is distributed to the stages by means of pulse transformers. The signal propagation within the stages has been equalized. The paper describes setup and testing of the switch.