GB859045A - Improvements relating to transistor or thermionic valve switching circuits - Google Patents

Abstract

859,045. Transistor and thermionic discharge tube circuits. ELECTRIC & MUSICAL INDUSTRIES Ltd. April 23, 1957 [April 19, 1956], No. 11919/56. Class 40(6). In a circuit for switching current in one or other direction through a load L a current path is arranged between high and low potential sources with the load connected to an intermediate point. The path includes the current paths of two transistors T1, T2 or thermionic discharge tubes, with coupling between them so that by applying a control signal to the input, one or other of the devices, T1, T2 may be rendered conducting. Assuming the input to the base of transistor T1 to be negative so that the transistor is fully conducting then a current passes through the emitter-collector path and network R1, C1 and load L. The fall in potential across resistor R1 is such that the base of transistor T2 is carried positive with respect to the emitter and the transistor remains cut off. With a positive input applied to transistor T1, it is cut off and the collector potential falls with the result that the base potential of transistor T2 also falls and the transistor conducts. Current now passes through load L the emitter-collector path of transistor T2 and the resistor R2. The resistors R1, R2 are chosen to define suitable values of current through the load L which may be a winding of a magnetic core matrix. The capacitors Cl, C2, and C3 are effective to reduce the time 1ag in the build up of current in the load.