GB1140684A — Switching circuits

USPTO Abstract

1,140,684. Transistor switching circuits. ROTAX Ltd. 29 July, 1966 [31 Aug., 1965], No. 37163/65. Heading H3T. A capacitor 3 charges from a supply at a rate dependent on the magnitude of a control signal until the potential across it is sufficient to operate a switching device 6 and develop an output across a resistor 7. The capacitor 3 is periodically discharged by means of a switching device 8 to interrupt current flow through resistor 7. The rate of charge of capacitor 3 is determined by the magnitude of the control signal at the base of transistor 1, which thus determines the time at which the potential across capacitor 3 renders transistor 5 conducting and breaks down Zener diode 6. When this occurs, positive feedback between transistors 1, 5 causes transistor 5 to saturate rapidly and produce an output across resistor 7. When transistor 8 is switched on by a pulse at its base capacitor 3 is discharged and the circuit switches to its other state for a time dependent on the amplitude of the signal at 10. If a train pulses is applied at 9, the output across resistor 7 comprises a train of pulses, the pulse width and hence the mean output voltage being dependent on the amplitude of the signal applied at 10.