High Current, Fast Turn-on Pulse Generation Using Thyristors

Abstract

The dynamic turn-on characteristics of inverter type SCR's can be employed to achieve high current densities with short rise times (106a/cm2µs). Little carrier modulation occurs during these turn-on times which results in large forward voltage drops. Resultant dissipations necessitate short pulse width operation but repetition rates up to 50KHz are reported. By comparing turn-on voltage waveforms of specially developed 35A (rms) devices when gate and dv/dt triggered, it was concluded that about 50% of the gate triggered emitter area is effective during the rise time interval. These devices were life tested and should prove usefull as modulators for radar or GaAs injection laser applications. It was determined that the properly designed SCR could out-perform all of the functions served by: 1) Avalanche transistors in laser pulsers, 2) Hydrogen thyratrons, ignitrons and spark gaps in radar modulators and, 3) High speed (turn-on) switching transistors where turn-off is not critical.