Schaltungsanordnung, die mindestens einen Thyristor mit einem Halbleiterkörper mit Basis- und Emitterschichten enthält

1,222,144. S.C.Rs. ALLMANNA SVENSKA ELEKTRISKA A.B. 25 June, 1968 [30 June, 1967], No. 30258/68. Heading HlK. An S.C.R. is provided with an ignition electrode and at least one bias electrode on one of its base layers, the bias electrode being supplied with a voltage such that the junction between the said base layer and the adjacent emitter layer is reverse biased at least during the blocking interval of the device. As shown, Fig. 2, an S.C.R. has a cathode electrode 6 and a central ignition electrode 97 contacting the adjacent base layer 4 which is also provided with three bias electrodes 91, 92, 93 which are connected together and biased negatively with respect to the cathode by source 12. The device is fired by applying a positive voltage to the ignition electrode 97. In a second embodiment, Fig. 3 (not shown), six bias electrodes are provided and each is connected to the central ignition electrode by means of a diode. The bias and ignition voltages are applied directly between the ignition electrode and the cathode and the diodes are poled so that negative bias applied to the ignition electrode is also applied to the bias electrodes but a positive firing voltage applied to the ignition electrode is blocked from the bias electrodes. The S.C.R. and diodes may be mounted in a single housing. In another embodiment, Fig. 4 (not shown), two bias electrodes and an ignition electrode are arranged round the periphery of the cathode region which is provided with a small notch to accommodate the ignition electrode and larger semicircular recesses to accommodate the bias electrodes. The ignition and bias electrodes are connected directly together and their arrangement relative to the cathode region ensures that when a positive firing voltage is applied conduction is initiated only at the point adjacent to the ignition electrode. The ignition electrode may also be positioned at the centre of the cathode. In a further embodiment, Fig. 5 (not shown), the ignition electrode is arranged to one side of the cathode region and a single, strip-like bias electrode surrounds the majority of the remainder of the cathode region. The bias electrode may be provided with an individual bias voltage source or may be connected directly to the ignition electrode in which case the thickness of the base layer between the bias electrode and the cathode is reduced by etching or blasting to ensure that conduction is initiated only at the ignition electrode.