GB972079A - Electronic pulse-generating circuit arrangements - Google Patents

Abstract

972,079. Transistor pulse circuits. ASSOCIATED ELECTRICAL INDUSTRIES Ltd. Feb. 15, 1962 [April 19, 1961], No. 14147/61. Heading H3T. A circuit for producing a pulse at the time of onset of an input pulse and a further pulse of the same polarity at the time of offset of the input pulse comprises a transistor TR2 having resistors R5, R6 in the emitter and collector circuits, the base being overdriven by the input pulse beyond the condition at which the base voltage becomes equal to the collector voltage. As described, the 50 c/s. output of transformer T1 is fed via an adjustable phase shifting circuit comprising resistors RV1, R2, and capacitors C2, C3, to a clipping circuit comprising diode D3 and transistor TR1. Positive half-cycles are clipped by D3 and negative half-cycles limited by TR1 so that the collector waveform of TR1 consists of positive-going pulses, the duration of which is equal to a halfcycle of the input sine wave. It is shown that when the NPN transistor TR2 is driven beyond the saturation point by these pulses the polarity of the collector waveform is reversed so that a negative-going pulse is generated each time the base current passes through the saturation point. The transistor TR3 and diode D4 are rendered conductive by each pulse from TR2 so that an amplified pulse is fed to the trigger electrode of a controlled semi-conductor rectifier (not shown), connected in series with the unsmoothed output of a full-wave rectifier. The output of the rectifier (not shown) is thus dependent on the timing of the control pulses and is hence adjustable by variable resistor RV1. The duration of the pulse fed to TR2 may be increased by a capacitor connected across the input of TR1, or by biasing the base of TR1. The D.C. supply to the circuit is provided by full wave rectifiers D1, D2 and stabilized by a Zener diode Z1.