I am creating a pulse generator. The requirement calls for a switch to be closed for 100ns, and open for for the remainder of a 500us cycle. The sampling rate of the transducer being driven by the pulse generator is 2kHz. hence 500us. The capacitor should discharge within 4 tau, which gives a 25ns time constant. The requirements call for a microcontroller to interface with the switch, in order to control exactly when the pulses are sent. I have tried diligently, but cannot find a switch that meets these requirements. In order to explain better I've posted a picture of the circuit. When the switch is closed, there should be a very low current flowing through the 560kohm, so the 100ns window the switch is closed shouldn't damage the transducer.