Setup and testing of a fast stacked-MOSFET switch

For experiments on electroporation of microalgae rectangular pulses with a pulse length of 20-100 ns and adjustable amplitude of up to 5 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 set-up and testing of the switch.