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Symmetrical Low Offset Transistor

IP.com Disclosure Number: IPCOM000082770D
Original Publication Date: 1975-Feb-01
Included in the Prior Art Database: 2005-Feb-28
Document File: 2 page(s) / 25K

Publishing Venue

IBM

Related People

Atwood, BC: AUTHOR

Abstract

This bipolar transistor structure is capable of acting as a switching device for positive and negative voltages, and is primarily useful in applying test voltages to integrated circuit devices.

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Symmetrical Low Offset Transistor

This bipolar transistor structure is capable of acting as a switching device for positive and negative voltages, and is primarily useful in applying test voltages to integrated circuit devices.

Conventional lateral bipolar transistors normally are fabricated as a closed structure, in which the collector completely surrounds the emitter. Such structures act as poor switches to different polarity voltage supplies as the ratio of collector/emitter perimeters, and therefore the forward and reverse beta, differ considerably for forward and reverse bias.

Fig. 1 shows a plan view of the planar transistor including comb-shaped emitter (collector) 10 and collector (emitter) 12. The region 14 between emitter 10 and collector 12 represents the base region. By providing symmetrical emitter/collector regions 10 and 12 the transistor will have relatively low-offset voltage, desirable for switching operations involving both positive and negative voltages. Fig. 2 is a schematic circuit showing the use of the transistor as a bidirectional switch.

The transistor may be fabricated by standard bipolar processing techniques, permitting both NPN and PNP devices on the same integrated circuit chip.

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