| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a stable control operation to a variation in temperature in an automatic gain control circuit for converting an optical signal to an electric signal, amplifying the signal to a prescribed level, and generating an output. <P>SOLUTION: The control circuit includes an APD1; a preamplifier 2; a variable gain amplifier 3; an amplitude detecting circuit 5; a temperature detecting circuit 13; a memory 10 for holding a reverse bias voltage to the APD1 in accordance with the temperatures, a current-voltage conversion gain control value to the preamplifier 2, and a gain table including a plurality of combinations of amplification gain control values to the variable gain amplifier 3; a register 9 for holding data in a temperature corresponding region of the gain table of the memory 10 according to the detection of temperatures; a comparator 7 for comparing the amplitude detected value and a reference value; a digital filter 8 for generating an address signal of the register 9 according to the comparison output signal; and D-A converters 13, 14, 15 for reading out from the register 9 according to the address signal and controlling the APD1, the preamplifier 2, and the variable gain amplifier 3. <P>COPYRIGHT: (C)2006,JPO&NCIPI |
