| 摘要 |
PURPOSE:To satisfy a tracking response and accuracy of display both, by variably controlling an envelope forming circuit with good display accuracy and a current value of a constant current source with a differential output having good response speed. CONSTITUTION:A diode 15, a capacitor 17 and a resistor 16 form an envelope forming circuit, and its envelope voltage Ee2 changes by following the envelope of an input Ein. Further the circuit constant of envelope forming circuit is selected by emphasizing the response in comparison with the accuracy. The output Ee2 is compared wth an output Ee of an envelope forming basic circuit 14 at a comparator 18 and the differential output Er controls the current value of constant current sources 9c and 10c. Thus, since the output Er is increased when the tracking of the circuit 14 is not followed, the response of the circuit 14 is improved by increasing the control current value of current sources 9c and 10c. On the other hand, when the tracking of the circuit 14 overtakes and the output Er is smaller, since the current value of the current sources 9c and 10c is decreased, the accuracy for the display output Ee can be assured. |
