| 摘要 |
PURPOSE:To prevent the deterioration of sound quality, by using the capacitor of small capacitance and good quality, by dividing the output of the amplifier through resistors and by negative feedback of the divided signal via a capacitor. CONSTITUTION:The output of the amplifier 2 is fed to the output terminal 3 and also branched into two; one is negative-fed-back to the inverting input terminal of the amplifier 2 via the resistor 8 and another is grounded via the series circuit of negative feedback voltage dividing resistors 4, 5, and negative feedback is made from the junction points of the resistors 4 and 5 to the noninverting input terminal of the amplifier 2 via the capacitor 7. In this circuit, the resistance value R8 of the resistor 8 is taken sufficiently greater value than the resistance values R4, R5 of the resistors 4, 5, and when the impedance of the capacitor 7 at an audible frequency band is regarded as zero, the low band cut-off frequency f3 is f3=1/[2piC(R5.R8)/ (R4+R5)] and the frequency is lower than a multiple of (R4+R5)/R8 in comparison with conventional systems. Accordingly, the degradation of sound quality can easily be prevented by using a capacitor of small capacitance and good quality. |
