NT & RP Journal
IMPACT OF FORWARD EMITTER CURRENT GAIN AND GEOMETRY OF PNP POWER TRANSISTORS ON RADIATION TOLERANCE OF VOLTAGE REGULATORS
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Vol. XXV, No. 3, Pp. 157-254
December 2010
UDC 621.039+614.876:504.06
ISSN 1451-3994

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Pages:
179-185

Authors:
Vladimir VukiŠ, Predrag V. OsmokroviŠ

Abstract

Low-dropout voltage regulators with various geometries and technological realisations of serial pnp power transistors were exposed to ionizing radiation. Although devices with vertical emitters were considered much less susceptible to the influence of radiation on forward emitter current gain than circuits with round emitters, the experiment showed a similar degradation of current gain in both cases. The main reason of high radiation susceptibility of the examined vertical serial pnp transistor is the implementation of an interdigitated emitter, with high perimeter-to-area ratio, causing the great increase of serial transistor’s base current, but a minor influence on the maximum output current. Transistors with round emitters with small perimeter-to-area ratio expressed a moderate current gain degradation, but a rapid fall of the emitter injection efficiency, causing a significant decrease of the maximum output current. Regardless of the similar forward emitter current gain degradation, reliability and operational characteristics of two types of low-dropout voltage regulators were completely different.

Key words: forward emitter current gain, power pnp transistor, lateral transistor, vertical transistor, voltage regulator, gamma radiation, quiescent current

FULL PAPER IN PDF FORMAT (989 KB)

Vinča Institute of Nuclear Sciences :: Designed by milas :: July 2007
Last updated on December, 2010