Solid-state 2 kV, 250 kHz grid modulator for traveling-wave tubes

A circuit has been developed utilizing high-voltage MOSFET switches in a series totem-pole configuration for driving TWT (traveling wave tube) grids. This system has been used at grid swings up to 1500 volts at 250 kHz, 2000 volts at 100 kHz and 2500 volts at 10 kHz. The pulser is entirely solid-state and is a high-efficiency design, using MOSFET-based switching power supplies to provide the pulse and bias voltages. The switching power supplies provide regulation accuracy of 0.1% for the basic pulse and bias voltages, and as a sample-and-hold circuit senses pulse current and adjusts the pulse supply upward to compensate for voltage drop in the series MOSFET switch. This allows pulse voltage regulation of not more than 3 volts over a pulse load range up to 400 mA.<>