Patent GB-783513-A (GB)
Title: Improvements relating to semiconductor devices
IPC: H03G1/00
Filed: 1954-01-19
Abstract: 783,513. Transistors. GENERAL ELECTRIC CO. Jan. 19, 1954 [Jan. 19, 1953], No. 1629/54. Class 37. [Also in Group XL (c)] A transistor comprises a semi-conductor body of one conductivity type, emitter and collector electrodes each formed by fusion to the body of an activator element characteristic of the opposite conductivity type to produce PN junctions in the body between which a first potential gradient is established and separated base electrodes between which is established a second potential gradient intersecting the first potential gradient, the source of potential establishing the second potential gradient being so connected that variations in its value do not affect the magnitude of the first potential gradient. In the Fig. 1 arrangement the body 6 is of N-type conductivity and blobs 2, 4 of acceptor activator form the emitter and collector electrodes. Batteries 3, 5 biasing these electrodes are connected to the earthed base electrode 8, while the second potential gradient is provided by battery 15. The forward bias of the emitter junction thus varies from point to point. When the potential of base electrode 10 relative to earth is increased in either direction the emission becomes progressively more localized at the part of the junction remote from the more positive electrode. Since the bulk of the collector current is derived from emission from the central part of the emitter junction the fraction of the total emitter current reaching the collector, i.e. the current gain a decreases with increasing field strength. The field, according to its direction causes a rise or fall of the mean potential of the material adjacent the junction, thus causing a decrease or increase respectively in the total emitter current, which may be compensated by adjustment of the bias. If the emitter junction is small compared with the collector (Fig. 2, not shown) carriers are collected almost uniformly from all parts of the emitter junction so that changes in distribution of emission affect α only slightly. If the emitter is made much larger than the collector (Fig. 3, not shown) only carriers from a narrow central zone reach the collector in quantity so that field has a strong influence on α, which also has a lower maximum value. In the Fig. 4 arrangement, where the emitter is nearer to base electrode 56 than is the collector the maximum α occurs when the opitmum emission occurs from a region at a distance below the middle of the junction, which increases with the distance apart of the emitter and collector in the direction joining the base electrodes, i.e. when base electrode 56 is positive, and α decreases with increase or decrease of the potential from that value. Since base resistance decreases in the presence of a field, this arrangement gives a maximum value of α when r b , and therefore the feedback, is low, so that α decreases only slowly with increasing frequency. High-frequency working is also improved since the effective emitter area and therefore the capacity is small at maximum α. The arrangement may be used as an amplifier with signal applied between emitter and base, between the two bases or between base 8 and earth, and the emitter or collector may be earthed instead of the base. By applying two signals, one between base and emitter and the other between the bases, as shown in Fig. 1, the device may operate as a multiplier or modulator. In the arrangement of Fig. 8, two collectors 74, 76 on one face of block 66 are symmetrically disposed with respect to a single emitter 72 on the other face. Load resistors 86, 88 respectively are connected between collectors 74, 76 and the bias battery, and -an input signal applied in series with the emitter bias. A source of control signals 92 varies the potentials of the bases so that by varying the distribution of emission the current gain of the two circuits may be varied, and the arrangement used for switching the input between the two output circuits. In Fig. 9 (not shown), there are two emitters, each with its own input circuit and a single collector so that either input can be switched to the collector. In either case the relative positions of the collectors and emitters may be varied to alter the characteristics of the system, and more than two collectors or emitters may be used in conjunction with one or more emitters and collectors respectively. In Fig. 12 (not shown), is shown a semi-conductor device as used in Figs. 8 and 9 arranged in a push-pull amplifier circuit. NPN junction devices may replace the PNP devices shown, in which case the polarities of emitter and collector bias stip. plies are reversed. Specification 700,236 is referred to.