GB1447998A - Current supply circuit - Google Patents

Abstract

1447998 Automatic current control ITT INDUSTRIES Inc 2 Nov 1973 [18 Nov 1972] 51021/73 Heading G3R A circuit for supplying constant current to an integrated circuit comprises a series supply transistor with its collector connected to the emitter of a multi-collector current distribution transistor. The current in one collector of the distribution transistor is compared with a reference value in a regulating circuit which provides a control signal to the base of the supply transistor. The reference value is derived from the base-emitter threshold voltage of at least one transistor. As shown in Fig. 1, transistors T1, T2 are connected in series across a dry cell battery supply voltage U B . Transistor T2 is of the multi-collector type, and a resistor R senses the current in one of the collectors and provides a control signal through a regulating amplifier V to the base of supply transistor T1 in order to keep constant the currents in each of the collector circuits of transistor T2. The other collectors may be connected to various stages of an integrated circuit containing an oscillator and frequency divider driving an electro-mechanical transducer. The voltage at the base of transistor T2 is fixed by a constant voltage device B, which may be one or more diodes, a Zener diode or a transistor. The amplifier V may use the baseemitter voltage of one or more transistors as a reference value, and additional transistors or groups of transistors may be connected with base-emitter paths in parallel with those of transistors T1, T2, Figs. 2-6 (not shown).