Photocurrent-to-voltage conversion apparatus including non-diode-connected clamping MOS transistor

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Quick Facts

Patent No.: US 7,045,762
App. No.: 10/900,185
Granted: May 16, 2006
Kind: B2

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Abstract

In a photocurrent-to-voltage conversion apparatus for converting a photocurrent flowing through a light receiving element into a detection voltage, an amplifier, a feedback resistor and a clamping MOS transistor are provided. The amplifier has an input connected to the light receiving element and an output for generating the detection voltage, and includes (2n+1) inverter stages connected in series where n is 1, 2 . . . . The feedback resistor and the clamping transistor are connected between the output and input of the amplifier. The clamping MOS transistor is controlled by an output voltage of a non-final inverter one of the inverter stages.

Claims (43)

1. A photocurrent-to-voltage conversion apparatus for converting a photocurrent flowing through a light receiving element into a detection voltage, comprising:

an amplifier having an input connected to said light receiving element and an output for generating said detection voltage, said amplifier including (2n+1) inverter stages connected in series where n is 1, 2 . . . ;

a feedback resistor connected between the output and input of said amplifier; and

a clamping MOS transistor connected between the output and input of said amplifier and being controlled by an output voltage of a non-final inverter one of said inverter stages.

2. The photocurrent-to-voltage conversion apparatus as set forth in claim 1 , wherein said light receiving element comprises a reversely-biased photodiode.

3. The photo current-to-voltage conversion apparatus as set forth in claim 1 , wherein said non-final inverter stage comprises an m-th inverter stage of said inverter stages where m is 2, 4, . . . , 2n, so that an absolute value of a gate-to-source voltage of said clamping MOS transistor is larger than an absolute value of a drain-to-source voltage of said clamping MOS transistor.

4. The photocurrent-to-voltage conversion apparatus as set forth in claim 3 , wherein said clamping MOS transistor comprises a clamping P-channel enhancement-type MOS transistor whose gate is connected to an output of said m-th inverter stage, and

wherein each of said inverter stages comprises a constant current source and an N-channel enhancement-type MOS transistor connected in series between a power supply terminal and a ground terminal.

5. The photocurrent-to-voltage conversion apparatus as set forth in claim 3 , wherein said clamping MOS transistor comprises a clamping N-channel enhancement-type MOS transistor whose gate is connected to an output of said m-th inverter stage, and

wherein each of said inverter stages comprises a P-channel enhancement-type MOS transistor and a constant current source connected in series between a power supply terminal and a ground terminal.

6. The photocurrent-to-voltage conversion apparatus as set forth in claim 1 , wherein said non-final inverter stage comprises an m-th inverter stage of said inverter stages where m is 1, 3, . . . , 2n−1, so that an absolute value of a gate-to-source voltage of said clamping MOS transistor is smaller than an absolute value of a drain-to-source voltage of said clamping MOS transistor.

7. The photocurrent-to-voltage conversion apparatus as set forth in claim 6 , wherein said clamping MOS transistor comprises a clamping P-channel enhancement-type MOS transistor whose gate is connected to an output of said m-th inverter stage, and

wherein each of said inverter stages comprises a constant current source and an N-channel enhancement-type MOS transistor connected in series between a power supply terminal and a ground terminal.

8. The photocurrent-to-voltage conversion apparatus as set forth in claim 6 , wherein said clamping MOS transistor comprises a clamping N-channel enhancement-type MOS transistor whose gate is connected to an output of said m-th inverter stage, and

wherein each of said inverter stages comprises a P-channel enhancement-type MOS transistor and a constant current source connected in series between a power supply terminal and a ground terminal.

9. The photocurrent-to-voltage conversion apparatus as set forth in claim 6 , wherein said clamping MOS transistor comprises a clamping N-channel enhancement-type MOS transistor whose gate is connected to an output of said m-th inverter stage, and

wherein each of said inverter stages comprises a constant current source and an N-channel enhancement-type MOS transistor connected in series between a power supply terminal and a ground terminal.

10. The photocurrent-to-voltage conversion apparatus as set forth in claim 6 , wherein said clamping MOS transistor comprises a clamping P-channel enhancement-type MOS transistor whose gate is connected to an output of said m-th inverter stage, and

wherein each of said inverter stages comprises a P-channel enhancement-type MOS transistor and a constant current source connected in series between a power supply terminal and a ground terminal.

11. A photocurrent-to-voltage conversion apparatus for converting a photocurrent flowing through a reversely-biased photodiode having a grounded anode and a cathode into a detection voltage, comprising:

an operational amplifier having an inverting input connected to the cathode of said photodiode, a grounded non-inverting input and an output for generating said detection voltage, said operational amplifier including (2n+1) inverter stages each formed by a constant current source and an N-channel enhancement-type MOS transistor connected in series between a power supply terminal and a ground terminal;