| 摘要 |
<p>A pre-amplifier (2) amplifies an output current of a photodetector (1) that converts a burst optical signal into an electrical signal, and outputs an electric voltage signal. A gain switching circuit (3) is connected with a serial circuit comprising a resistor (6) and a switch (9) and a serial circuit comprising a resistor (7) and a switch (10), in parallel with a feedback resistor (2b). The gain switching circuit (3) includes an arrangement to receive the electric voltage signal output from the pre-amplifier (2), close the switch (9) at a specific bit position, close the switch (10) at the other specific bit position, upon occurrence of a situation that the switch (10) is to be closed, provided that the switch (9) is closed. <IMAGE></p> |
