| 摘要 |
PURPOSE:To attain the increase of the amount of boosting by constituting a low frquency boost circuit with a negative feedback CR filter so as to produce a peak at the vicinity of a cut-off frequency. CONSTITUTION:A signal component having a frequency being a cut-off frequency f0 or over in an audio signal e0 applied to the low frequency boost circuit is attenuated by 6dB by a low pass filter comprising resistors R4, R5 and a capacitor C3. Further, the signal is amplified by an amplifier circuit comprising a transistor (TR), the amplified signal is fed back negatively to a resistor R5 via a capacitor C5 and a signal component having a frequency being the f0 or over is attenuated further by 6dB by a low pass filter comprising the resistor R5 and the capacitor C3. Then, since the larger peak at the vicinity of the cut-off frequency f0 is provided when the smaller the capacitance ratio (m) of the capacitor C3 to the C5 is, the signal component having a frequency being the f0 or over is attenuated by an attenuation >=12dB by decreasing the capacitance ratio (m). |
