Patent GB-677969-A (GB)
Title: Improvements in or relating to relay devices using semi-conductive devices
IPC: H03K3/313
Filed: 1951-02-14
Abstract: 677,969. Semi-conductor amplifiers. WESTINGHOUSE ELECTRIC INTERNATIONAL CO. Feb. 14, 1951 [March 17, 1950], No. 3576/51. Class 40 (iv). [Also in Groups XXXVI, XL (b) and XL (c)] A transistor has a load impedance in the collector electrode and bias voltages applied to the emitter and collector of such values that the collector current/collector voltage characteristic intersects the load line at two points at least the emitter current being modified to cause the collector characteristic to intersect the load point at one point only so that the collector current jumps instantaneously from one value to a substantially different value. Fig. 3 shows a transistor comprising a block 11 of N-type semi-conductive material having a small inclusion 13 of P-type material on one face, the collector 15 being located in contact with the inclusion 13 and near the P-N boundary of the block 11. An output impedance 18 is included in series with a variable collector positive bias source 23, which may be an A.C. source and the emitter 29 is connected via an input impedance 31 to a variable bias source 37. It is shown in Fig. 4 that if collector current is plotted against collector voltage and load lines C, B, &c. are drawn for varying collector voltages then by adjustment of the location and pressure of the collector probe 15 and at a given value of negative bias on the emitter a collector characteristic curve E may be obtained which intersects the load line B at three points c, d and e. If a positive pulse is applied across the input impedance 31 which effectively raises the collector characteristic peak voltage to, for example, that of characteristic G then load line B intersects this characteristic only at point e and the collector current changes instantaneously from its original value at point c to its new value at point e. The circuit may be restored by reducing the collector voltage or by connecting the circuit to operate as a relaxation oscillator as shown by means of capacitor 45 and resistor 43. The circuit will also automatically restore if an A.C. collector bias source is employed and the circuit can thus function as a free-running or triggered relaxation oscillator. The circuit may be adjusted so that it is triggered by either positive or negative input pulses and a P-type block having an N-P or N-type inclusion may be biased positively from source 37. Fig. 5 shows a modification in which a normal N-type transistor is used, the collector 51 being biased negatively to a voltage EC 3  as shown in Fig. 6, and the bias of the emitter 49 is made sufficiently positive so that the collector characteristic curve L intersects the load line H at three points h, k, n. The circuit may then be triggered by application of a positive pulse across the input impedance 55 so that a characteristic curve M is obtained and the collector current changes instantaneously from the value at point h to that at point n. The circuit may be re-set as described in connection with Fig. 3 and may thus operate as a triggered or free-running relaxation oscillator. A P-type element may be used when the polarities will be reversed. The circuit shown in Fig. 3 may be triggered by a change in the ambient temperature in the vicinity of the emitter which increases the resistance in the emitter circuit thus decreasing the emitter current and in effect decreasing the emitter bias so that the collector characteristic peak voltage is reduced and the collector current rapidly jumps to a new value. The emitter bias may be adjusted so that the device is triggered by either a rise or fall in temperature and may thus be used as a thermally-sensitive relay. A P-type block with an N-type inclusion or a normal N or P- type element without any inclusion may also be used to achieve the same results. The Specification also describes a photo-peak diode, Figs. 1 and 2 (not shown), comprising an N- type body with a P-type inclusion which has a collector voltage/current characteristic curve which exhibits a peak and the position of which may be altered by variation of the ambient temperature or of the intensity of light falling on the probe-inclusion junction region.