Arbitrary Lifetime Research Articles

Reliability of a Repairable System with Standby Failure

This paper deals with a system in which one unit is operating online and is backed my m spares as warm standbys. There are r repair facilities. The on-line unit has an arbitrary lifetime distribution, while the spares have exponential failure time distributions. The repair time distribution is also exponential. This problem, viewed as a queuing problem, cannot be solved; but by locating a set of renewal points, we write the equations governing the states of the system and calculate the reliability and availability. Explicit results are obtained in the case of five redundant units and three repair facilities.

Reverse transient characteristics of a P-N junction diode due to minority carrier storage

Analysis of the transient switching characteristics of a p-n junction diode is considered a boundary value problem; solution of this problem yields mathematical equations applicable to the design of high-speed computer components. This analytical technique is used to establish the transient current of a semiconductor diode when an external biasing potential is rapidly switched from the forward to the reverse direction. Using a one-dimensional model of finite geometry, minority-carrier storage is assumed within a region of arbitrary lifetime, bounded on one side by the junction and on the other side by an ohmic contact of arbitrary recombination velocity. Further, this region of carrier storage is assumed to contain a drift field of constant magnitude as would result from an exponential type of conductivity grading. Mathematical equations are presented which characterize this transient situation from its initiation until the junction current has decayed to some arbitrary magnitude. Applications of this analysis are illustrated in graphical form throughout a range of parameters characterizing practical semiconductor devices.

On the theory of DC amplification factor of junction transistors

According to Webster's phenomenological theory, the base current consists of three terms arising from 1) surface recombination 2) bulk recombination, and 3) non-unity emitter efficiency. In this paper, the diffusion equation inside the base region of an alloyed transistor is solved, and an analytic expression for the dc amplification factor is presented in terms of arbitrary bulk lifetime and surface-recombination velocity and the geometry of the transistor. The surface-recombination term depends on the distribution of the injected carriers along the emitter-base boundary, and hence, it increases as the emitter current increases on account of the base-resistance bias effect which tends to concentrate the minority carriers near the periphery of the emitter. The falloff in beta at high-emitter current is attributed mainly to an increase in the surface-recombination term, contrary to Webster's theory. A comparison with Webster's theory is made on units having the same bulk property but different surface treatments. Experimental results give strong support to the present theory.