| 摘要 |
PURPOSE:To raise the response speed by using an inverting operational amplifier connected in the negative feedback type and inserting a diode in series between a transmission line and the input of this amplifier and controlling a DC current flowed to this diode in accordance with the level of a pilot signal. CONSTITUTION:Generally, the gain of an inverting operational amplifier 7 is determined by Z2/Z1. A resistance RI is used as the element having the impedance Z2, and a combinational circuit of diodes D1-D4 is used as the element having the impedance Z1, and the DC current flowed to diodes D1-D4 is varied in accordance with the level of the pilot signal, and the operating resistance is varied to perform the AGC operation. Thus, with respect to relations among the output level of the pilot signal, DC currents IC1 and IC2, and the gain of the amplifier 7, currents IC1 and IC2 are reduced to reduce the gain of the amplifier 7 when the output level of the pilot signal is raised. In this case, the response speed of the AGC operation is raised because the operating resistance of diodes is changed quickly. |
