FEEDING CIRCUIT OF SUBSCRIBER SYSTEM

摘要

PURPOSE:To attain ease of circuit integration by using a feedback loop so as to cancel noise from a power supply thereby preventing the noise from the power supply from giving effect on a subscriber system circuit without the use of an LPF. CONSTITUTION:The noise of the power supply V is divided into 1/4 by four resistances R16-R19 and given to subtraction circuits 12, 13. On the other hand, a noise voltage reduced to a half at the connecting point of the resistances R17 and R18 is fed to the input terminal of a voltage follower amplifier 14 via a resistance R20 and the noise voltage without any change is outputted therefrom. Said noise voltage is fed to a connecting point between the resistances R13 and R14 and it is divided further into 1/2 by the resistances R12, R13 and R14, R15. The noise voltage reduced into 1/4 by the resistances R16, R12, R15 is fed to the substration circuits 12, 13, cancelled with the noise voltage from the resistances R16, R19 and then no effect is given on transistances Tr1, Tr2. Thus, the LPF to eliminate the noise from the power supply voltage V is not required.