Patent GB-1400688-A (GB)
Title: Master-slave transistor bistable circuit
IPC: H03K23/58
Filed: 1973-04-05
Abstract: 1400688 Frequency divider; shift registers ITT INDUSTRIES Inc 5 April 1973 [8 April 1972] 16273/73 Headings G4A and G4C [Also in Division H3] In a master-slave bi-stable circuit comprising a master stage TM1, TM2 and a slave stage TS1, TS2 each consisting of cross-coupled transistors which have their emitters connected together, a coupling stage TK1, TK2 connecting the master stage to the slave stage and an input gate TG1, TG2 connecting the master stage to the inputs A, B, the master stage, the slave stage, the coupling stage and the input gate each consist exclusively of transistors of the same conductivity type, the input gate for each bistable half consists of a transistor TG1, TG2 whose base is connected to the interconnected emitters of the master stage transistors, whose collector is connected to the collector of the associated master stage transistor and whose emitter is D.C. connected to the associated input and a clock pulse T is applied to the emitters of the master stage transistors and to the bases of the input gate transistors. The master stage TM1, TM2 and slave stage TS1, TS2 are D.C. connected to one another via the coupling stage TK1, TK2, only when the clock pulse is below a first threshold voltage (UK, Fig. 2, not shown) and the inputs A, B are D.C. connected to one another via the input gate TG1, TG2 only when the clock pulse is above a second higher threshold voltage (U G ). The threshold voltages are exceeded in turn during the rise time of a clock pulse applied at T and the clock pulse amplitude falls below the thresholds in turn during the fall time of the clock pulse. The coupling stage TK1, TK2 includes for each bi-stable half a transistor with its emitter connected to the collector of the associated master stage transistor, with a further electrode connected to the collector of the associated slave stage transistor and with its base and collector connected via constant current sources (not shown) or via resistors (not shown) to a current supply I. The collector of the master stage transistors TM1, TM2 are connected to the current supply I via constant current sources (not shown) or via resistors (not shown).  As shown the outputs Q, #Q are taken from the collectors of the slave transtors TS2, TS1 or may be taken from the collectors of double emitter transistors TK1, TK2 forming the coupling stage. Further transistors TZ1, TZ2 may be included so that the bi-stable circuit can be preset or reset by input to C, D. The circuit can be constructed in integrated form. A plurality of circuits may be connected to form a shift register (Fig. 4, not shown) or a frequency divider (Fig. 5, not shown). In an integrated circuit of a frequency divider embodiment one or more stages can have a switch (S) which may be a further transistor controlled from outside the integrated circuit and associated with the slave transistor connected to the output double emitter transistor so that by closing this switch the division ratio of that stage can be made 1. In this way the required division ratio can be selected. When the above bi-stable circuits are used in a shift register the two double emitter transistors TK1, TK2 may be replaced by a respective transistor having its emitter connected to the collector of the associated master transistor and its collector connected to the collector of the associated slave transistor.