| 摘要 |
PURPOSE:To prevent a signal of proper amplitude from being influenced by a signal of excessive amplitude by connecting a switch circuit, which turns on when the amplitude of a control signal exceeds amplitude limit range, in parallel to the discharge resistance of a time constant circuit. CONSTITUTION:When the amplitude of an input signal exceeds the reference amplitude value and stays within the amplitude limit range, time constant circuit 5 supplies variable attenuating circuit 3 with a control voltage that provides attenuation equivalent to an excess over the reference amplitude. After the signal is removed, the control voltage is discharged with the time constant determined by capacitor 8 and resistor 7 and when the control voltage reaches a threshold voltage equivalent to the preset reference amplitude, the attenuation of circuit 3 is ceased. Once a signal of amplitude exceeding the amplitude limit range is input, the rectification output accumulated in capacitor 8 is rapidly discharged with the time constant, determined by the capacity of capacitor 8 and the conductive resistance of Zener diode 10, until it reaches the Zener voltage. |
