Temperature compensated avalanche photodiode optical receiver circuit
First Claim
1. An avalanche photodiode circuit comprising:
- an avalanche photodiode for receiving a light signal and generating an electrical output in response thereto;
a thermistor-containing voltage divider network; and
a first resistor; and
whereinsaid voltage divider network is electrically separated from said avalanche photodiode except for said first resistor which is connected therebetween.
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Abstract
A photodiode receiver circuit having self-contained automatic gain control and which is temperature compensated over a wide operating range contains a resistor coupled in series between a bias power supply and one end of an avalanche photodiode. Self-generated AGC action results from the fact that the gain of an avalanche photodiode increases as the bias voltage applied across the diode increases. As the light intensity received by the diode increases, there is a corresponding increase in the current flow through the diode and the series-connected resistor. The consequential increase in IR drop across the resistor decreases the bias voltage across the diode, so that the gain of the diode is reduced. Through this action, the dynamic range of optical input of the photodiode will be increased for a fixed dynamic range of electrical output.
Temperature compensation is achieved by coupling a temperature-sensitive voltage divider circuit between the bias voltage supply and the gain-controlling resistor. This voltage divider network may include a thermistor coupled in parallel with one resistor component of a resistor divider that is connected to a bias voltage source. The value of the parallel resistor is chosen to match the thermistor'"'"'s characteristic to the voltage versus temperature characteristic of the APD so that a temperature-compensated bias voltage reference, to which the gain-controlling resistor is connected, is available over a wide temperature range (e.g. -40° C. to +60° C.). This temperature compensation allows the avalanche photodiode to be operated at a nearly constant available gain across this range and prevents the diode from being damaged by too high a bias voltage.
165 Citations
13 Claims
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1. An avalanche photodiode circuit comprising:
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an avalanche photodiode for receiving a light signal and generating an electrical output in response thereto; a thermistor-containing voltage divider network; and a first resistor; and
whereinsaid voltage divider network is electrically separated from said avalanche photodiode except for said first resistor which is connected therebetween. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. An opto-electrical conversion circuit comprising:
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an opto-electrical conversion element for receiving a light signal input and generating an electrical output in response thereto; a gain control element; and a negative temperature coefficient variable resistance network connected to a source of bias potential; and
whereinsaid network is electrically separated from said opto-electrical conversion element except for said gain control element which is connected therebetween for controlling the voltage bias applied across said conversion element in response to the electrical output generated in accordance with the light signal applied to said conversion element, whereby the gain available to said conversion element is maintained substantially constant over a prescribed temperature range. - View Dependent Claims (9, 10, 11, 12, 13)
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Specification