| 摘要 |
PURPOSE:To obtain a pre-emphasis and a de-emphasis circuit applied effectively to a PCM recording and reproducing device especially by changing the characteristic in response to a signal through the use of a multiplying D/A converter. CONSTITUTION:A resistor 3 and a switch 5 form a multiplying D/A converter 33, a capacitor C is provided in series with the resistor 3 to form a variable pre-emphasis circuit. When the value of the D/A converter 6 is small, a switch 5 is turned on to allow the resistor 3 and the capacitor 4 to emphasize the high frequency characteristic of the amplifier 2 of the feedback circuit. A resistor 9, a switch 11 and a capacitor 10 form similarly a de-emphasis circuit to attenuate the high frequency characteristic of the amplifier 12. Through the constitution above, the characteristic is changed easily in response to the signal amplitude, then the optimum characteristic is obtained in case applying the circuit to the PCM recording and reproducing device especially. |
