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Decode Transistor

IP.com Disclosure Number: IPCOM000076879D
Original Publication Date: 1972-Apr-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 2 page(s) / 103K

Publishing Venue

IBM

Related People

Baker, TH: AUTHOR [+3]

Abstract

The practice of having multiple emitters 1 in a common-base diffusion 2, as illustrated in Fig. 1, is subject to both horizontal 3 and vertical 4 parasitic NPN effects. Common procedures used to minimize these parasitic effects are the use of gold-doping and/or an increase of the horizontal distance 5 between the emitters.

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Decode Transistor

The practice of having multiple emitters 1 in a common-base diffusion 2, as illustrated in Fig. 1, is subject to both horizontal 3 and vertical 4 parasitic NPN effects. Common procedures used to minimize these parasitic effects are the use of gold-doping and/or an increase of the horizontal distance 5 between the emitters.

Fig. 2 illustrates how to eliminate both the horizontal and vertical parasitic effects for a decode transistor, in which the base-collector junction is to be shorted for its circuit function so that it only requires a diode drop (see Fig. 3), and which has no H(FE) requirements. The presence of the highly doped isolation diffusion 6 for the common-base region of the transistors reduces the emitter efficiency for both parasitic NPN transistors, and thus reduces parasitic transistor action.

An added benefit is more efficient use of silicon area, since the distance 5 between the emitter regions can now be reduced by approximately 30%.

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