GB752678A - Mono-stable multivibrators - Google Patents

Abstract

752,678. Pulse generating circuits. RADIO CORPORATION OF AMERICA. April 13, 1954 [April 29, 1953], No. 10881/54. Class 40 (6). A flip-flop circuit comprises two intercoupled electron tubes which have a large value capacitor connected between the cathodes and a degenerative resistor connected between the cathode of the normally non-conductive tube and a point of fixed potential. By this means the amplitude and duration of the output pulse generated are stabilized against changes caused by variations in tube characteristics and power supply voltage. Fig. 1 shows a flip-flop circuit in which tube V1 is non-conductive and tube V2 conductive in the stable state and in which the circuit is triggered to its unstable state by positive pulses applied to the grid of tube V1 at terminal 12. A large value capacitor 25 is connected between the cathodes of tubes V1 and V2 and a large resistor 16 is included in the cathode circuit of tube V1 the time constant of network 25, 16 being at least 20 times the maximum period between applied trigger pulses. The resistor 16 is much larger than cathode resistor 24 and is considerably in excess of that required for self-biasing of tube V1. The grid of tube V2 is normally biased to the conductive state by resistor 21. The duration of the positive output pulses generated at the anode of tube V2 is primarily determined by the time constant of resistorcapacitor network 19, 21. In a modification shown in Fig. 4 the grid of tube V1<SP>1</SP> and the timing resistor 21<SP>1</SP> are both connected to the junction point 32 of resistors 13<SP>1</SP>, 21<SP>1</SP> the potential of which is maintained constant during the cycle of operation by by-pass capacitor 33.