GB778152A - Improvements in or relating to transistor flip-flop circuits - Google Patents

Abstract

778,152. Transistor one and two stable state and gating. circuits. PHILIPS ELECTRICAL INDUSTRIES, Ltd. Feb. 15. 1955 [Feb. 18, 1954], No. 4499/55. Class 40(6) In a circuit comprising two transistors 1, 2 and resistors 3, 4 each resistor is common to the collector circuit of one transistor and to the base circuit of the other and in at least one stable state the emitterbase paths of the two transistors are conducting, one of the transistors being traversed by a collector current so high that owing to the drop of the collector voltage the collector-base current amplification factor drops below unity. The emitters of the transistors are connected to one pole of the supply and base resistors 5, 6 are connected to the transistors 1, 2. In one stable state the transistor 2 passes heavy current so that the working point is at a, Fig. 2 the voltage drop across resistor 3 together with that across resistor 5 due to the base current of transistor 1, biasing transistor 1 to the point b. Input signals applied at terminal 7 to the base of transistor 1 are amplified using the load line R and appear at terminal 9. The circuit may be switched from one stable state to the other by signals applied at terminals 7 or 8. Resistor 10 may be the internal impedance of a switching source. By increasing the value of the resistor 5 and decreasing the resistor 4 the circuit may be made mono-stable. A pulse applied at terminal 7 triggers transistor 1 to point a and transistor 2 to point b. Due to the choice of component values the circuit is only maintained in this state until the: input capacitor has charged sufficiently when the circuit reverts to its normal state.