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Magnetic Transistor DC Offset Voltage Balance Control

IP.com Disclosure Number: IPCOM000046097D
Original Publication Date: 1983-May-01
Included in the Prior Art Database: 2005-Feb-07
Document File: 3 page(s) / 47K

Publishing Venue

IBM

Related People

Vinal, AW: AUTHOR

Abstract

An inherent DC output voltage offset potential will be measured at the collectors of a magnetic transistor of the bipolar lateral NPN or PNP type. Such transistors are described and illustrated in Electronics, 45-46 (May 19, 1982). It is well known that many magnetic sensors do not permit simple elimination of the offset voltage that is produced at the sensor output levels by processing irregularities in constructing the devices, etc. A Hall cell is one such example for which no easy balancing method at the level of the device itself exists. Instead, for a Hall cell, additional amplification for one or another of the output voltages is required.

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Magnetic Transistor DC Offset Voltage Balance Control

An inherent DC output voltage offset potential will be measured at the collectors of a magnetic transistor of the bipolar lateral NPN or PNP type. Such transistors are described and illustrated in Electronics, 45-46 (May 19, 1982). It is well known that many magnetic sensors do not permit simple elimination of the offset voltage that is produced at the sensor output levels by processing irregularities in constructing the devices, etc. A Hall cell is one such example for which no easy balancing method at the level of the device itself exists. Instead, for a Hall cell, additional amplification for one or another of the output voltages is required.

The type of transistor described in the referenced article provides an opportunity for a much simpler method of balancing out the offset potentials produced.

In Fig. 1, a typical magnetic transistor structure is shown in plan view. A substrate 1 of P-type semiconductor material is provided with an emitter 2 and an emitter contact 3 which is connected to ground for an NPN device. Diffused collectors 4 are laterally placed on either side of the diffused emitter 2, as illustrated. Appropriate metal contacts 3 and 5 for the emitter and for the two collectors are also included. Two base regions 6, generally outlined in a rectangular area but not comprising a diffusion, are also illustrated located laterally beside each collector and axially aligned therewith. Electrical contacts 7, which are of the ohmic variety, are provided for each of the base areas. It is important to note that each of the base contacts is positioned relative to its adjacent collector such that it is in back of the collector relative to the collector and the emitter. By connecting one of the base contacts, for example, the one on the right hand side of the emitter in Fig. 1, minority carriers injected vertically from the bottom surface of the emitter 3 will exhibit an injection density gradient from the left to right hand across the surface of the emitter. The end closest to th...