GB808663A - Improvements relating to time base circuit arrangements employing transistors - Google Patents

Abstract

808,663. Transistor circuits for generating sawtooth waves. BRITISH THOMSONHOUSTON CO. Ltd. Feb. 26, 1957 [March 8, 1956], No. 7307/56. Class 40 (6). A time base voltage generator comprises a capacitor, means for charging the capacitor to generate voltage sweeps and a discharge transistor connected across the capacitor, the input and output circuits of the transistor being coupled by a transformer which, when the transistor is rendered conductive, rapidly causes saturation to occur in the transistor so that the discharge path has a low resistance. As shown, a capacitor C1 is charged through a transistor T1 connected so as to maintain the charging current constant. When the potential on the lower electrode of the capacitor passes beyond that of the bias E3 at the base of a transistor T2, the latter transistor begins to conduct and due to the coupling between the collector and base circuits through the transformer L rapidly saturates. Accordingly, the capacitor C1 is rapidly discharged. Synchronizing pulses are applied to the base of transistor T2 through capacitor C3 and a diode D prevents overswing of the transformer voltage. The circuit may be converted into one of single stroke type by increasing the value of the base bias of transistor T1 so that charging of capacitor C1 stops before the transistor T2 becomes conductive. The charging rate may be varied by adjusting resistor R3 or changing value of capacitor C1.