| 摘要 |
PURPOSE:To establish the AGC circuit excllent in SN ratio and greater in the dynamic range, which consists of differential amplifier and photo coupler. CONSTITUTION:The transistors TR1, TR2 to which load resistors RL1, RL2 and emitter resistors RE1, RE2 are connected, constitute the differential amplifier having the input terminals e1, e2. Between the emitters of the both trnansistors, the resistor R1 of photo conductive cell of photo coupler is connected. Further, the resistor R1 is changed by the AGC voltage V fed to LED of photo coupler and the gain of the differential amplifier is controlled with this. The emitter potential of the transistors TR1, TR2 is of equi-potential independently of the change in the resistor R1 and no non-linear distortion of differential amplifier can be increased. |
