Transient Response of Drift Transistors

The short-circuit transient response of a drift transistor is found for a step of input current. The one-dimensional partial differential equation for minority carriers in the base is solved by a Laplace transform technique yielding the rise, storage, and fall times in the common-emitter and common-base configurations. The improvement in rise time due to the built-in field in a drift transistor is found to be less in the common-emitter than in the common-base configuration, which in turn is found to be less than the improvement previously predicted. The built-in field is shown to lengthen storage time, but other effects of the field such as low αІ1 tend to cancel this out in a practical transistor.