Patent GB-751595-A (GB)
Title: Transistor circuits
IPC: H03K21/00
Filed: 1953-09-25
Abstract: 751,595. Transistor two stable state circuits. INTERNATIONAL BUSINESS MACHINES CORPORATION. Sept. 25, 1953 [Sept. 30, 1952], No. 26445/53. Class 40 (6). [Also in Group XIX] The emitter-base path of a transistor in a trigger circuit is arranged in series with a further transistor having a load impedance connected in the collector lead. In the OFF state, tube 26, Fig. 2, is non-conducting so that there is no current flowing in the emitter circuit and hence the collector circuit of transistor 34. The potential of line 22 is thus at a low value so that the grid of tube 26 is maintained below cut-off. A positive pulse on line 22 causes tube 26 to conduct thereby raising the emitter potential so that current flows in the emitter and collector leads, the potential of line 22 rising sufficiently to maintain tube 26 in the conducting or ON state. A negative pulse on line 22 resets the circuit to the OFF state. Since the impedance of the collector circuit is relatively high, resistors 10, 12 are given high values so that no appreciable load may be imposed on them without affecting switching speed. A second transistor 36 is therefore employed feeding the output load resistor 38. Counter circuit. A number of trigger circuits ST1 ... ST4, Fig. 1, together with a further circuit ST5 may be combined to form a biquinary counter. Input-square waves, Fig. 3, are applied over a differentiating circuit 42, 43, negative pulses being suppressed by diode 46 to give a train of short positive pulses on line 44. Assuming all the circuits are in the OFF state, the settings of potentiometer 38 are arranged so that the first pulse, fed over capacitor 45 to potentiometer 12 causes circuit ST1 to go over to the ON condition. The resulting rise in potential of the tap on potentiometer 38 primes ST2 which passes to the ON condition upon the receipt of the next pulse. The process is continued with the third and fourth pulses. The fifth pulse causes normally non-conducting tube 52 to pass current which drives the grids of all the tubes 26 negative, resetting ST1 ... ST4 to the OFF state. The base of transistor 60 is also driven negative so that it passes current, the rise in collector current causing the grid of tube 61 to rise and anode current to flow so that circuit ST5 remains ON. The succeeding four pulses operate ST1. ST4 and the fifth is effective to reset them. The pulse from tube 52 is ineffective in increasing the base current of transistor 60 but as it is also applied to the grid of tube 61 it causes a reduction of current in the tube which effect is increased due to the pulse being fed to the collector of transistor 60 to reduce current in potentiometer 66 so that circuit ST5 passes to the OFF state. An output pulse is derived from the cathode of tube 61. The pulses fed from resistors 10a, 10b are sharpened by differentiating circuit 70, 77, diode 78 suppressing any negative-going waveform. A tube 86 is paralleled with tube 26 so that when the circuit is ON, both conduct, tube 86 causing neon 80 ... 83 to glow. When ST5 is ON, grounded grid tube 90 is cut off so that the anode potential rises sufficiently for neon 84 to fire. Capacitor 95 is effective to shorten the resetting time of circuits ST1 ... ST4 and capacitors 96, 97 delay the rise in priming potential to prevent a second circuit operating on a single input pulse. A resistor 98 increases the priming bias fed to the next stage. All the circuits may be reset by temporarily increasing the negative potential of line 16. By attaching a differentiating circuit 57, 58 at an appropriate point suitably spaced pulse waveforms appear at terminal 59. Trigger circuit operated and reset by pulses of the same polarity. In a modification, Fig. 4, the tube 26 is arranged between the transistors 34, 36 and diodes 109, 106 are arranged to pass only negative pulses to the base of transistor 34 to trigger to the ON state and to the grid of tube 26 to reset to the OFF state. The output is taken from the collector load 38 but may also be taken from the emitter. Capacitors 100, 101 are arranged to provide a delay. Specification 722,516 and U.S.A. Specification 2,623,170 are referred to.