Magnetically responsive resistance device
US 3082507 A
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Description (OCR text may contain errors)
March 26, 1963 F. KUHRT ETAL MAGNETICALLY RESPONSIVE RESISTANCE DEVICE, PARTICULARLY HALL GENERATOR Filed NOV. 20, 1956 United States Patent Ofifice 3,082,507 Patented Mar. 26, 1963 3,082 507 MAGNETICALLY RESPbNSIVE RESISTANCE DEVICE, PARTICULARLY HALL GENER- ATO Friedrich Kuhrt and Karl Maaz, Numberg, Germany,
assignors to Siemens-Schuckertwerke Aktiengesellschaft, Berlin-Siemensstadt and Erlangen, Germany, a corporation of Germany Filed Nov. 20, 1956, Ser. No. 623,415 Claims priority, application Germany Jan. 7, 1956 1 Claim. (Cl. 29155.5)
Our invention relates to electric variable resistance devices which vary their resistance in dependence upon the effect of a magnetic field. The resistance body proper of such a device is located within a gap of an electromagnet or permanent magnet and, when in operation, is traversed by an electric current whose direction of flow extends transverse to the magnetic field or a component thereof.
Suitable as material for the magnetically responsive resistance body in such devices are semiconductors,'preferably the semiconducting compounds of the type A B that is, compounds of an element A from the third group with an element B from the fifth group of the periodic system of elements. Such semiconducting compounds are, for instance, indium antimonide, indium arsenide, indium phosphide, gallium antimonide and gallium arsenide, the compounds indium arsenide and indium antirnonide being most advantageousbecause of their extremely high carrier mobility. Particularly great changes of electric resistance under the effect of a magnetic field have been observed with such compound materials. When using such magnetically responsive resistors of the compound type for the production of Hall voltages, the devices have the further advantage that the Hall voltage output can be directly supplied to a current-consuming load without breakdown of the Hall voltage and hence without the necessity of using voltage pre-amplifiers for many purposes. I Because of this capability of supplying an appreciable Hallpower output, such devices are often referred to. as Hall I generators.
It has been found, however, that when such magnetically responsive resistance devices, particularly Hall generators, are operated with alternating or periodic electric currents or magnetic fields, the performance may leave much to be desired and involves undesired losses if the current or field frequency is relatively high. Similar phenomena, although to a lesser extent, have been observed with the usual powerline frequencies of 50 or 60 c.p.s.
It is an object of our invention to minimize such deficiencies and to reduce the losses encountered when operating at higher frequencies.
We have found that the losses and disturbances are essentially due to the occurrence of eddy currents within the magnet-field responsive resistance body and that these phenomena are greatly reduced or virtually eliminated by providing a plurality of elongated resistance members of small width relative to their length, locating these members side-by-side in the air gap of the magnetic field structure, and interposing preferably high-ohmic resistors between the current supply terminals, formed on the opposite ends of the elongated members, and the leads that supply current to said terminals. We further electrically connect these resistance members in parallel relation to each other with respect to the flow of controlling current, and also interconnect the members in series relation to each other with respect to the Hall potentials of the individual members.
According to another feature of the invention the individual magnetically responsive resistance members above mentioned are formed from a single resistor structure by slitting it from opposite sides in the direction of the electric current flow to approximately the middle of the structure In this manner, a single coherent resistor body is provided which, as regards its functioning, is equivalent to a plurality of individual resistance members that are parallel connected in the current supply circuit but series connected with respect to the resulting Hall voltages.
The foregoing and other objects and features of our invention will be apparent from the embodiment described in the following and illustrated on the drawing in which:
FIG. 1 shows a multiple-member resistor structure of a device according to the invention;
FIG. 2, illustrates an electric circuit diagram applicable with such a device; I 7
FIG. 3 illustrates a modification of a multi-member resistor structure, and
FIG. 4 shows a complete Hall generator embodying the features of FIGS. 1 and 2.
Referring first to FIG. 4, the illustrated device comprises a magnetic field structure composed of a magnet core 20 joined with two pole pieces 21 and 22 whose respective pole faces are spaced from each other to form a gap in which a semiconducting resistor structure or Hall plate 1 of generally rectangular shape is disposed. The core is shown provided with a magnetizing coil 13 by means of which the field strength in the gap occupied by resistor structure 1 can be varied to thereby change the electric resistance between the terminals (4e and Se in FIG. 4) of the body. As explained, the resistor structure 1 consists preferably of indium antimonide or indium arsenide. Its design and an example of suitable circuit connections are apparent from FIGS. 1 and 2. The overall size of the rectangular structure 1 depends upon the resistance and power requirements. For example, the overall length may be 12 mm., the width 8 mm., and the thickness of the plate ile., wafer, corresponding to the thickness of the pole gap, may amount to 15 microns.
As apparent from FIG. 1, the resistance body 1 is equipped with Hall electrodes 2 and 3 as well as with current supply terminals denoted by 4a to 4g and 5a to 5g. The body 1, originally forming a massive rectangle, is provided with slits 6 which extend from both sides in the current-flow direction to nearly the middle of the body and thus subdivide the body into a number of individual resistor members which are all series connected at their 7 respective midpoints relative to the Hall electrodes 2, 3.
The subdivision of the rectangular shape has the effect of reducing the Width of each component Hall member so that the power losses are also reduced to a considerable extent.
In order to prevent eddy currents from finding a closed, low-resistance circuit extending through the current supply leads and the Hall-voltage connections of the component Hall members, it is necessary to connect the current-supply terminals 41: to 4g and 5a to 5g with the current-supply leads through resistors, preferably highohmic resistors interposed, between the electrodes and the leads. Such a connection is illustrated in FIG. 2. The controlling current, passing from the supply terminals 7a and 712 through the Hall plate structure, is supplied to the individual terminals 4a to 4e and 5a to Sc through respective high-ohmic resistors 8a to 82 and 9a to 9e.
In a magnetically responsive resistance device according to the invention, the eddy current losses are so extremely slight that the magnetic-field responsive resistor, according to another feature of the invention, can be used as an amplifier because the controlling power supplied to the magnetic field, for instance in form of a variable excitation current passing through the coil 13, can be kept smaller than the power output taken from across the Hall electrodes 2 and 3. Such a Hall amplifier, with a suitable circuit connection, can also be used as an oscillation generator. For this purpose, and as shown in FIG. 2, the controlling magnetic field Winding 13 and a capacitor 14 may be connected into the Hall-electrode circuit between the electrodes 2 and 3. The power output of the device may be taken from across the same electrodes 2 and 3. However, it is also possible to use as the variable output magnitude the voltage across the winding 13 or across the capacitor 14.
In some cases, according to still another feature of our invention, it is preferable to use'high-ohmic resistors 8a to tie and 9a to 9c in form of granular-mass resistors and to connect them directly with the current supply terminals of the magnetically responsive resistor members. The embodiment illustrated in FIG. 3 is of this type. The mass resistors 18a to 18e and 19a to 19c are directly attached to the current supply electrodes of the individual component members of the magnetically responsive resistor body 1. The ends of the mass resistors that face away from the body 1 may all be interconnected by a single conducting terminal layer 11 or 12 that extends over all individual resistor members located at the same side of body 1. The conducting layers 12 and 13 serve preferably as a connecting terminal for the current supply leads coming from terminals 7:; and 7b. The mass resistors consist preferably of amorphous carbon material, for instance graphite.
The Hall electrodes 2, 3 as well as the terminals 4a to 4g, a to 5g as well as the connecting conductor layers 11, 12 may consist of copper or silver.
The following method has been found advantageous for the manufacture of the magnetic-field responsive resistance device shown in FIG. 3. A rectangular resistance body of magnetically responsive material, such as indium arsenide or indium antimonide, is first provided at both narrow sides with respective extensions consisting of a mass of high-ohmic resistance material, preferably graphite. The resistance mass, having the same width and thickness as the semiconductor body, thus forms marginal extensions along the two short sides of the rectangular shape. Thereafter, the composite rectangular body is slitted from both sides toward the middle, thus simultaneously producing the individiual current-carrying members as well as the high-ohmic resistors connected therewith. The ends of the high-ohmic resistors facing away from the magnetically responsive resistance body are subsequently covered with a conducting layer which extends over all resistor bodies on the same side of the assembly, as shown in FIG. 3, and which may serve as a connecting terminal common to all individual current paths. 7
By virtue of the invention the eddy current losses of magnetic field-responsive resistance devices are reduced to such a great extent as to become negligible for most purposes; and it will be obvious to those skilled in the art that the invention is not limited to the particular embodiments herein described but will produce similar advantages when modified as regards the shape of the resistor assembly and/or the electric circuit connections of the device.
It is understood that the terms ohmic resistance means and high-ohmic resistors signify that said means or resistors have a higher resistance than the semiconductor plate.
The method of producing a magnetic-field responsive semiconductor device having opposite current terminal ends, which comprises the steps of joining a high-ohmic resistance material with a water of magnetic-field responsive semiconductor material on the two opposite current terminal end-s of the wafer, thereafter slitting the highohmic material and the wafer from said two ends toward but not across a middle portion of the wafer, whereby a group of parallel partial wafer members is produced, and then depositing on each of said two ends an electroconductive layer onto the high-ohmic material on said ends of all of said members and across the slits.
References Cited in the file of this patent UNITED STATES PATENTS 1,778,795 Craig Oct. 21, 1930 1,778,796 Craig Oct; 21, 1930 2,464,807 Hansen Mar. 22, '1949 2,752,434 Dunlap June 26, 1956 2,835,866 Vradenburgh et a1 May 20, 1958