GB915762A - Improvements in or relating to transistor bistable circuits - Google Patents

Abstract

915,762. Transistor bi-stable circuits. BUDTS, L., DE ROUMEFORT, F. DE S., and DE ROUMEFORT, (nee BALIGANT) J. DE S. Aug. 6, 1959 [Aug. 8, 1958; June 12, 1959], No. 26900/59. Class 40 (6). [Also in Group XL (b)] A bi-stable circuit comprising two transistors cross-coupled has a capacitor associated with one transistor so that, in the absence of an input, the circuit automatically assumes a preferred state when it is switched on. Fig. 3 comprises two transistors T 1 , T 2 having their base and emitters cross-connected so that the device has two stable states in which one or other of the transistors is conducting. A capacitor C ensures that when power is first applied to the circuit, in the absence of a control signal, it assumes the state in which T 1 is conducting. A switch I 1 , when operated, will cause the circuit to change its state and, when I 2 is open, opening switch I 1 will restore the circuit to its initial state. Operation of I 2 on its own will not change the state of the circuit but if I 1 and I 3 are both operated the circuit will hold the new state even if I 1 is released. The switches I 1 and I 2 may be constituted by the emitter collector circuits of transistors, the base of which may be connected to a light-sensitive cell (Fig. 5 and 6, not shown). The output from E may be applied to a further bi-stable circuit (Fig. 6, not shown), or to an amplifier (Fig. 9, not shown). Fig. 11 shows an alternative circuit in which a capacitor C 1 is connected in series with a resistor to the base of transistor T 2 to ensure that on first switching on, in the absence of a switching signal, transistor T 1 becomes conducting. Switching is effected through line X or X 1 and a diode D is provided to increase the sensitivity. Multiple outputs are obtained from parallel connected resistors 104, 105 and 106 or 101, 102 and 103, though in Fig. 16 (not shown), these resistors are replaced by diodes. Alternative coupling arrangements comprising diodes and series capacitors so that only impulses are passed are described with reference to Figs. 12-15 (not shown). These arrangements may be combined to form " AND," " OR " and " INHIBIT " connections (Fig. 17, not shown), and to perform other logic functions (Figs. 19-21, not shown). Coupling between a number of stages and a number of further stages may be effected by a single diode together with a number of resistors (Fig. 7, not shown), or by a number of diodes operating in parallel (Fig. 8, not shown). In addition to light-sensitive input elements magnetic induction sensitive elements, contactmaking switches or thermally-sensitive resistors may be used as the input switching elements and the output may be coupled through magnetic amplifiers to electromagnetic switching devices (Fig. 10, rot shown).