GB1211792A - Voltage stabilisers - Google Patents

Abstract

1,211,792. Automatic voltage control. STANDARD TELEPHONES & CABLES Ltd. March 21, 1968, No.13713/68. Heading G3R. A voltage regulator comprises an input terminal 2, an output terminal 3 and a common input/output terminal 1; a first transistor Tr1 having its emitter/collector path connected in series between terminals 2, 3 and having its base connected to terminal 1 over a resistor R1 and the collector/ emitter path of a second transistor Tr2; and a second resistor R2 connected to the base of transistor Tr2 which base is also connected to the common terminal 1 via the collector/emitter path of a third transistor Tr3 having its own base connected to the output terminal 3 over a resistive element, e.g. a Zener diode Z. When an unstabilized voltage is applied to terminals 1, 2 the transistor Tr1 is automatically controlled in known manner to maintain a constant voltage across terminals 1, 3 and the Specification explains how the particular arrangement described provides this stabilized output until the applied voltage falls to a value which exceeds the required stabilized output by a value less than the potential drop between the emitter and collector of transistor Tr1, and also continues to provide an unstabilized output when the applied voltage has dropped below the voltage required to give the stabilized output. A variable resistor P may be connected between the base and emitter of transistor Tr3 to provide for adjustment of the stabilized output voltage, and a capacitor may be connected between the collector and base of transistor Tr2 to damp the feedback signal and prevent hunting.