Light-receiving circuit

• US 20060027736A1
• Filed: 08/08/2005
• Published: 02/09/2006
• Est. Priority Date: 08/09/2004
• Status: Active Grant

• Current Assignee: Sumitomo Electric Industries Limited (Sumitomo Corporation)
• Original Assignee: Sumitomo Electric Industries Limited (Sumitomo Corporation)
• Inventors: Ichino, Moriyasu, Hayashi, Sigeo
• Granted Patent: US 7,265,333 B2
• Time in Patent Office: Days
• US Class Current: 250/214.R
• CPC Class Codes: H01L 31/02027 for devices working in avalanche mode

Abstract

The present invention is to provide a light-receiving circuit, in particular, the circuit for an avalanche photodiode (APD), in which the current of the APD is dynamically controlled to protect the APD from the over current. The circuit comprises the high voltage source, the current mirror circuit connected to the high voltage source, the APD connected to one of the current output terminal of the current mirror circuit, and the current source connected to the other current output terminal of the current mirror circuit. The current flowing out from the other current output terminal is dynamically controlled by the current source to protect the APD from the over current.

Claims

1. A light-receiving circuit for receiving an input optical signal, comprising:

a voltage source for providing a voltage output;

a first current mirror circuit having an input terminal for receiving said voltage output from said voltage source, a current setting terminal for providing a bias voltage, and a current mirroring terminal;

an avalanche photodiode for receiving said input optical signal, said avalanche photodiode being connected to said current mirroring terminal of said first current mirror circuit to receive said bias voltage; and

a current source connected to said current setting terminal of said first current mirror circuit, said current source generating a reference current,

wherein said bias voltage varies so as to have said reference current set by said current source flowing in said avalanche photodiode.

2. The light-receiving circuit according to claim 1,

wherein said reference current set by said current source is determined to reflect said bias voltage provided to said avalanche photodiode.

3. The light-receiving circuit according to claim 2,

wherein said current source includes a reference resistor, and a transistor connected between said current setting terminal of said first current mirror circuit and said reference resistor, said transistor outputting said reference current such that a voltage generated in said reference resistor due to said reference current corresponds to said bias voltage.

4. The light-receiving circuit according to claim 2,

further includes a PIN-photodiode for receiving a portion of said input optical signal to output a monitored current, said reference current set by said current source reflecting said monitored current.

5. The light-receiving circuit according to claim 4,

further includes a first reference resistor connected in serial to said PIN-photodiode to convert said monitored current generated in said PIN-photodiode into a reference voltage,

wherein said current source includes a second reference resistor and a transistor connected between said current setting terminal of said first current mirror circuit and said second reference resistor, said transistor outputting said reference current such that a voltage generated in said second reference resistor due to said reference current corresponds to said reference voltage generated in said first reference resistor.

6. The light receiving circuit according to claim 5,

further includes a limiting circuit configured to limit said reference voltage.

7. The light-receiving circuit according to claim 6,

wherein said limiting circuit includes a diode and a third resistor connected in parallel to said diode, said diode and said third resistor being each connected in serial to said first reference resistor, said diode cramping said reference voltage.

8. The light-receiving circuit according to claim 4,

further includes a second current mirror circuit having a current setting terminal and a current mirroring terminal, said current setting terminal being connected to said PIN-photodiode, said current mirroring terminal being connected to said current setting terminal of said first current mirror circuit,

wherein said monitored current generated by said PIN-photodiode is reflected in said reference current flowing in said avalanche photodiode through said first and second current mirror circuits.

9. The light-receiving circuit according to claim 1,

further includes a feedback control circuit or lowering said voltage output of said voltage source by receiving said bias voltage.

10. The light-receiving circuit according to claim 9,

wherein said feedback control circuit includes a differential amplifier for receiving said bias voltage and a voltage of said current setting terminal of said first current mirror circuit and for controlling said voltage source such that said voltage of said current setting terminal becomes substantially equal to said bias voltage.

11. The light-receiving circuit according to claim 10,

wherein a closed-loop gain of said feedback circuit including said voltage source, said first current mirror circuit, and said feedback control circuit is 2 to 5.