Theory and applications of a three dimensional multiplier by means of magnetoresistance

There are many practical applications of galvanomagnetic effects of metallic and intermetallic semiconductors in electronic devices, most of them utilizing the Hall effect. On account of its characteristics as a two dimensional multiplier in nature and its simple circuit assembly, the Hall effect element has attracted more attention than the magnetoresistance element which needs inevitably an extra biasing magnetic field of a considerable magnitude to improve the non-linearity of its characteristic. In order to overcome this shortcoming a type of push-pull arrangement with 2 magnetoresistance elements in circuit is recommended, and the result is a three dimensional multiplier. A few examples of the applications of this kind of multiplier will be described in the paper, such as: (1) analog computing element which may carry out a large number of mathematical operations, (2) poly-phase power meter which is capable of showing the total power, (real, reactive, or apparent), in an electrical network with a single indication, (3) amplifiers and oscillators, (4) mixer, modulator and demodulator, (5) de current transformers, etc. In comparison with similar devices based on Hall effect, the magnetoresistance electronic devices have the advantages of higher sensitivity, better efficiency, and facility for adjustment. All the devices will be operating at ordinary room temperature. The construction of the magnetoresistance element will be discussed and some experimental results will be given.