| 摘要 |
PURPOSE:To flow no current to an earth line, by establishing the relation of a constant ratio determined by a gain between an output load resistance and a resistance which determines the gain. CONSTITUTION:A voltage signal (ei) is amplified by a noninversion amplifier 36 and an inversion amplifier 46 and is supplied to an output load resistance RL4. Both amplifiers are driven by positive and negative power sources. A gain A1 of the noninversion amplifier 36 is determined by a feedback resistance r2 and a feedback split resistance r1, and a gain A2 of the inversion amplifier 46 is determined by a feedback resistance r4 and an input resistance r3. When RL=A1.A2.r1 is true so that a current I1 flowed from the output terminal of the noninversion amplifier 36 to the earth point through the feedback resistance and a current I3 flowed from the earth point to the inversion amplifier 46 through the load resistance RL4 are equal to each other, no current is flowed to the earth line to prevent degradation of the tone quality. |
