Electrical and Computer Engineering ETDs

Publication Date

Summer 5-27-1966

Abstract

Excerpt from the Introduction:

The three terminal PNPN switch which we will refer to as the semiconductor controlled rectifier or SCR has electrical characteristics quite similar to the gas thyratron [7]. In the SCR, current is carried by electrons and holes whereas, in the thyratron, it is carried by electrons and ions. Both have high impedance in the "off" state and low impedance in the "on" state. Both devices will remain in the conducting mode once they have been triggered, even if the gate signal is removed.

The operation of the SCR depends upon the internal feedback mechanism [ 22]. In order to switch to the conducting mode the current gain must exceed unity, a concept that was first suggested by Shockley in his description of the "hook" collector [ 28]. Ebers [7] then developed a two transistor analogy of the SCR and showed that the anode current should go as, I~1/1-(α1+α2), where α1 and α2 are the common base· current gains of transistors one and two respectively. When α1+α2 < 1, the SCR will be "off", and when α1+α2 > 1, it will be "on". As with the junction transistor, SCR operation is dependent upon voltage, current, temperature, charge density and other parameters. If any of these parameters are varied sufficiently the SCR will switch to the conducting mode. Most SCR's are designed to be operated by controlling the gate current, but some special purpose SCR's are designed to be sensitive to light, tempera­ture, etc. In this report we are concerned with their be­havior in an ionizing radiation environment.

There are three widely used methods of analyzing transients in semiconductor devices, particularly in transis­tors The first developed was the large signal method of Ebers and Moll [3]. In 1957 Beaufoy and Sparks [2] developed their charge control model. In 1958 Linvill [16] published his development of the lumped parameter model. Hamilton, et al [11], showed that all three models are equivalent with regard to overall degree of approximation and therefore yield the same results in the solution of large-signal transient problems. Hence, the choice for a particular problem should depend primarily on the ease of application. We will use the basic concept of charge control in our analysis.

Document Type

Dissertation

Level of Degree

Doctoral

First Committee Member (Chair)

Wayne Willis Grannemann

Second Committee Member

Harold Dean Southward

Third Committee Member

William Jackson Byatt

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