High-speed power devices with field control

A generation of high speed power devices is appearing in which some fundamental deficiencies of transistors were overcome. Injection devices with better characteristics are bipolar transistors for high pulse currents but low voltages and for high voltages but low currents with switching frequencies up to 20 kHz. New devices are field effect transistors and electrostatically-controlled thyristors. Field-effect transistors are MOS devices featuring high speed with nanosecond switching time, high input impedance, small control current, and a negative temperature coefficient of drain current. Structurally they are produced with either vertical or horizontal conduction channel, both versions operating by the same principle and their cost still being high. Electrostatically-controlled thyristors are structurally produced with either surface grid or buried grid, the switching characteristics are better but the gain is lower with a surface grid. New devices are compared and it is revealed that GTO thyristors have the highest load capacity and field effect transistors have the highest switching speed.