| 摘要 |
PURPOSE:To prevent the generation of overload of an AGC amplifier circuit by using a peak detection voltage obtained from an output of the 1st stage amplifier so as to apply the gain control of the post-stage FET amplifier thereby applying the gain control of the post-stage amplifier independently of the DC balance of the polarity. CONSTITUTION:An additional amplifier circuit 4 is provided, which is equipped with a FET amplifier whose source potential is controlled by an output detection voltage of the 1st-stage amplifier 4-1 obtained by a peak detection circuit 6 as the post-stage amplifier 4-2 so as to give a peak detection voltage to a gate- source circuit of the post-stage FET amplifier. Through the circuit above, the peak value of the 1st stage output of the additional amplifier is detected to control a VSG of the next-stage FET amplifier thereby controlling the gain of the amplifier. Thus, the overload of the substantial AGC amplifier is prevented and the dynamic range of an amplifier circuit for optical reception is increased. |
