| 摘要 |
PROBLEM TO BE SOLVED: To make reduction of power consumption and a elimination of an inductor possible by excluding a voltage difference between a pair of output wires caused by an earth potential noise. SOLUTION: A line circuit has a 24V resistive power supply circuit having two pairs of outputs (a pair of output R2 and T2 and another pair of output R1 and T1) between an earth potential and -48V. Then, all the noises on the earth potential including an audio voltage are added to a ring (R2) by way of a capacitor C1, a Darlington emitter follower Q1 and Q2 and a resistor R11. The same earth potential noise signal is added to an output T2 by way of a capacitor C2, a source follower amplifier A1 and a resistor R13, to an output R1 by way of the capacitor C2, the source follower amplifier A1 and a resistor 14 and to a output T1 by way of a source follower Q10 and a resistor R17. A power supply noise on a -48V wire is blocked by a Darlington filter circuit consisting of transistors Q1 and Q2, voltage divider resistors 1R1 and 1R2 and the capacitor C1. |
