Browse Prior Art Database

Magnetic Switch or Magnetometer

IP.com Disclosure Number: IPCOM000092285D
Original Publication Date: 1968-Nov-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 41K

Publishing Venue

IBM

Related People

Fang, FF: AUTHOR [+3]

Abstract

This surface magnetic field device employs two field effect transistors FET's that are connected back-to-back so that their source-drain currents are in opposite directions. Thus the conductance in one FET, under given magnetic fields, increases, while the conductance in the other FET decreases. By choosing appropriate operating points for the two FET's, two states having the same current for two different values of magnetic field are obtained.

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Magnetic Switch or Magnetometer

This surface magnetic field device employs two field effect transistors FET's that are connected back-to-back so that their source-drain currents are in opposite directions. Thus the conductance in one FET, under given magnetic fields, increases, while the conductance in the other FET decreases. By choosing appropriate operating points for the two FET's, two states having the same current for two different values of magnetic field are obtained.

Drawing 1 shows a FET comprising source 1, drain 2 and control gate 3 with electrodes 4, 5, and 6 attached for connection to electrical energy sources not shown. If a magnetic field H is applied tangentially to the FET structure, the source-drain conductance I(SD) is modified as in drawing 2. An increasing field H increases the value of I(SD) and a decreasing field H diminishes its value.

Drawing 3 shows schematically how two FET's 7 and 8 are connected back- to-back so that their respective source-drain currents I(SD) and I(SD) oppose each other. By choosing appropriate voltages, biases, and other operating parameters for each FET, FET 7 has an I-H characteristic shown by curve 9 and FET 8 has the I-H characteristic 10 in drawing 4. Dotted curve 11 is the composite I-H curve of the two back-to-back FET's. Thus the device of drawing 1 has two magnetic field values represented by points X and Y for the same value of current.

The device can be used as a magnetometer, obtaining changes in I(SD)...