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Multiple Transistor Current Sharing

IP.com Disclosure Number: IPCOM000084504D
Original Publication Date: 1975-Nov-01
Included in the Prior Art Database: 2005-Mar-02
Document File: 2 page(s) / 36K

Publishing Venue

IBM

Related People

Beesley, JP: AUTHOR [+2]

Abstract

This circuit employs a multiple leg transformer to derive and apply collector current balancing signals to the bases of a corresponding number f parallel connected transistors. The drawing shows three transistors 10, 12, 14 in parallel combination. Therefore, the sharing transformer This circuit employs a multiple leg transformer to derive and apply collector current balancing signals to the bases of a corresponding number of parallel connected transistors. The drawing shows three transistors 10, 12, 14 in parallel combination. Therefore, the sharing transformer shown is a "3-phase" (i.e., three leg 16, 18, 20) type. The turns ratios between base windings and emitter windings determine the gain of the transformer in suppressing differences in collector current.

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Multiple Transistor Current Sharing

This circuit employs a multiple leg transformer to derive and apply collector current balancing signals to the bases of a corresponding number f parallel connected transistors. The drawing shows three transistors 10, 12, 14 in parallel combination. Therefore, the sharing transformer This circuit employs a multiple leg transformer to derive and apply collector current balancing signals to the bases of a corresponding number of parallel connected transistors. The drawing shows three transistors 10, 12, 14 in parallel combination. Therefore, the sharing transformer shown is a "3-phase" (i.e., three leg 16, 18, 20) type. The turns ratios between base windings and emitter windings determine the gain of the transformer in suppressing differences in collector current.

Magnetomotive forces (MMF's) are generated in legs 16, 18, 20 as a result of a small inequality of ampere turns in windings 22 vs 24, 26 vs 25 and 30 vs 32, such that the low-current transistors are turned on harder because of increased V(be). This constitutes feedback to minimize the error. These MMF's compare in the transformer in such manner as to induce corrective components in windings 24, 28, 32.

The principle employed is that collector current is emitter current minus base current. Therefore, the base and emitter windings of the respective transistors are connected to provided opposite MMF's. The resulting MMF is, therefore, proportional to the collector current....