An involute gate-emitter configuration for thyristors and transistors

In power thyristors and transistors, it is important to inject or remove carriers uniformly and rapidly across the entire junction area. Among the reasons are: 1.) the switching losses are reduced, thus allowing a higher load current rating of the device, 2.) a thyristor becomes capable to turn-off the load current by gate control, thereby eliminating commutating components and their losses. Uniform carrier injection or withdrawal and other desirable side effects are accomplished by a gate (base) emitter interdigitation in the form of equidistant involutes of a circle.