| 摘要 |
PURPOSE:To prevent the runaway and oscillations of an AGC loop system by limiting a bias current by inserting a resistance into the bias supply circuit of a DC/DC converter which supplies a bias voltage to an avalanche photo diode. CONSTITUTION:This photo receiver circuit consists of DC/DC converter 5 which applies a bias voltage to avalanche photo diode APD1, amplifier 2 which amplifies the output of APD1, and peak detector 3 which detects the peak value of the output of this amplifier 2. Further, operational amplifier 4 is provided which compares the peak value detected by detector 3 with reference voltage Ref and then applies this comparison output as a control voltage to the input of converter 5. Resistance R is inserted into the bias supply circuit of converter 5 of this constitution and a voltage across this resistance R is fed back to amplifier 4 by way of amplifier 6 and non-linear response circuit 7 to limit a current flowing through APD by way of resistance R, thereby preventing the runaway and oscillations of loop 2. |
