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Saturation Controlled Transistors

IP.com Disclosure Number: IPCOM000079174D
Original Publication Date: 1973-May-01
Included in the Prior Art Database: 2005-Feb-26
Document File: 2 page(s) / 25K

Publishing Venue

IBM

Related People

Wiedman, SK: AUTHOR

Abstract

The saturation of a transistor is controllable by an auxiliary transistor, if the base-collector junctions of both transistors are connected in parallel and the base-emitter junction of the auxiliary transistor is shorted. If a double-emitter transistor is employed, the emitter area of the auxiliary transistor has to be much larger than the emitter area of the actual transistor, so that a satisfactory reduction in the stored charge is obtained when the transistor is operated in heavy saturation.

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Saturation Controlled Transistors

The saturation of a transistor is controllable by an auxiliary transistor, if the base-collector junctions of both transistors are connected in parallel and the base-emitter junction of the auxiliary transistor is shorted. If a double-emitter transistor is employed, the emitter area of the auxiliary transistor has to be much larger than the emitter area of the actual transistor, so that a satisfactory reduction in the stored charge is obtained when the transistor is operated in heavy saturation.

In order to decrease the silicon area and the parasitic depletion-layer capacitances of the transistor, the circuit of Fig. 1 is used. By introducing a small resistor R between the bases of auxiliary transistor T2 and saturation controlled transistor T1, the excess base current supplied to the base of T2 is taken over by the emitter of T2 acting as a collector, even in cases where the emitter area of T2 is smaller than that of T1.

The layout of the double-emitter transistor (Fig. 2) shows the common N collector region with collector contact C, a P base region with base contacts B1 and B2, and the two N emitter regions with emitter contacts E1 and E2. The base region between base contacts B1 and B2 serves as resistor R. The device is isolated by a surrounding P+ isolation region.

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