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This paper describes the development of a semiconductor based switch for use in pulsed power technology. Because of the more stable operating conditions, given by the semiconductor devices, this switch could be used to replace the up to now in pulsed power technology common used spark gaps. We defined a technical concept for a semiconductor based switch with a maximum voltage of 20 kV and a current capability in the order of 1 kA. This concept also should enable to generate pulses widths of a few [micro]s. We found an IGBT with a maximum blocking voltage of 1700 V, a signal rise time of 100 ns, and a short circuit current rate of 650 A to be suited to realize our concept for the switch. Because of the defined maximum voltage of 20 kV it was necessary to use a series connection of the IGBTs. To ensure a synchronous switching of the in series connected devices, a trigger unit was built up which was inductively connected to the driver circuits of the single IGBTs. Single devices where tested and separated for the series connection. With the handicap of a given 155 mm circuit board we designed a complete switch, basing on industrial standards, with 15 IGBTs and a finally maximum blocking voltage of 18 kV, and a current capability of 500 A. The design of this circuit also included the development of a protecting circuit (active clamp) to protect the single devices of an over voltage damage during the switching, and also to avoid an inhomogeneous split up of the voltage to the different devices. Index Terms--IGBTs, pulsed power, series connection.