Patent GB-794753-A (GB)
Title: Improvements in or relating to electrical translating apparatus including a semiconductor
IPC: G01D5/18
Filed: 1955-09-19
Abstract: 794,753. Semi-conductor devices; electric analogue calculating systems; power measurement; magnetic tests. WESTINGHOUSE ELECTRIC INTERNATIONAL CO. Sept. 19, 1955 [Sept. 28, 1954], No. 26692/55. Class 37. [Also in Group XXXVIII] A semi-conductor apparatus comprises a thin, rectangular, semi-conductor body mainly of material of one type conductivity in which the ratio of majority to minority carrier density is less than 10: 1 with a region of the opposite type on at least one of two opposite edges forming a PN junction therewith, a source of control current connected to current electrodes on the other two edges of the body, means for biasing the junction or junctions in the reverse direction and means for producing a magnetic field to deflect current carriers towards or away from the or one of the junctions to provide a current in an output circuit. In the device shown in Fig. 1 the junctions are produced by the crystal growth or alloying methods on a body 101 of slightly N-type Ge, Si or AIIIBV compound (particularly one of the nine compounds of Al, Ga, In with P, As, Sb). When subjected to a magnetic field perpendicular to the plane of the paper with the D.C. source 103 connected as shown between, e.g., soldered ohmic electrodes 105, 107, both holes and electrons are deflected towards junction 111 and away from junction 113. Both junctions are reverse biased by battery 119 so that only minority carriers, i.e. holes cross then to produce output voltages across resistors 121, 123. Electrons accumulate at junction 111 and provide a space charge effect assisting the magnetic field in deflecting minority carriers. In the absence of a field some minority carriers cross both junctions, the effect of the field being to enhance the flow across junction 111 and reduce that across 113, to give an output voltage across terminals 125, 127 proportional to field strength and input current. The magnitude of the field may be measured if a constant amplitude A.C. source replaces source 103, and the device may be used as a multiplier in a computer if one variable is expressed as a magnetic field and the other as a current. A mainly P type body may alternatively be used with appropriately poled bias supplies. In either case the ratio of majority to minority carrier density should not exceed 10: 1. The device has the advantage over a Hall plate that the output is roughly independent of the size of the semi-conductor plate. An embodiment using the device in a temperature measuring system is also described (see Group XXXVIII). Power measurement.-The circuit shown in Fig. 3 uses a device as described above to measure power in an A.C. circuit. The load 344 in the circuit is wired in series with the energizing winding 330 of electromagnet 332 in the air gap of which the semi-conductor body is situated, while the ohmic electrodes 305, 307 are connected across the load to receive a current proportional to the instantaneous voltage across it. Separate junction bias supplies 319a, 319b are used, application of unwanted A.C. bias from the load being prevented by connecting said batteries to the centre taps of potentiometers 318, 320 connected across electrodes 305, 307. The output voltage across terminals 325, 327 is integrated by capacitor 348 co-operating with D.C. voltmeter 346 which indicates power.