Browse Prior Art Database

Semiconductor Magnetic Field Sensor

IP.com Disclosure Number: IPCOM000084224D
Original Publication Date: 1975-Oct-01
Included in the Prior Art Database: 2005-Mar-02
Document File: 2 page(s) / 49K

Publishing Venue

IBM

Related People

Freeman, LB: AUTHOR [+2]

Abstract

This is a magnetic field sensor (Hall effect device) comprising a field-effect transistor (FET) having a pair of drain regions of approximately equal area. The drains are separated by a region of a lower doping level, which is essentially a continuation of the channel region of the gate electrode. Carriers under the gate region of the FET are deflected to one or the other of the drain regions, depending upon the direction of the magnetic field which is perpendicular to the plane of the carrier current.

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Semiconductor Magnetic Field Sensor

This is a magnetic field sensor (Hall effect device) comprising a field-effect transistor (FET) having a pair of drain regions of approximately equal area. The drains are separated by a region of a lower doping level, which is essentially a continuation of the channel region of the gate electrode. Carriers under the gate region of the FET are deflected to one or the other of the drain regions, depending upon the direction of the magnetic field which is perpendicular to the plane of the carrier current.

Fig. 1 shows a perspective view of the device 10 formed in a substrate 1. The device comprises conventional source region 4, gate insulator 3 over the channel region and suitable metallic electrodes. The drain regions are denoted by the numerals 2 and 2'.

Fig. 2 shows a typical circuit in which the device is used for sensing overloads within a semiconductor integrated circuit chip. The circuit maintains the drain voltages substantially constant for relatively large changes in the drain currents. Transistors Q1 and Q2 act as source followers having their gate voltages fixed at V1 and their sources connected to the electrodes of drains 2 and 2', respectively. The drain voltages are, therefore, held at a threshold drop below V1 and will vary substantially with drain currents. However, relatively large output voltages are generated at the drains of Q1 and Q2 by using large load resistors R1 and R2. The latter may be field-effect tran...