| 摘要 |
The present invention provides a light-receiving circuit that protects the breakdown of the avalanche photodiode (APD) by the photo current. The light-receiving circuit of the present invention includes the current detection circuit that senses the photo current generated by the APD, and, when the photo current exceeds a predetermined threshold, the current detection circuit turns on voltage dropping circuit for the high-voltage source. Accordingly, the bias voltage VAPD applied to the APD is decreased to the value at which the APD does not show a show the carrier multiplication.
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