JP6323921B2 - Optical receiver circuit - Google Patents

Description

  The present disclosure relates to an optical receiving circuit that receives an optical signal and outputs it as a voltage signal.

  An optical signal output from a light emitting device such as a semiconductor laser is received by an optical receiver as disclosed in Patent Document 1. FIG. 1 is a diagram for explaining a main part of an optical receiver as described in Patent Document 1. The optical receiver includes a photodiode (PD) 51 that converts an optical signal into a current signal (photocurrent), an optical receiver circuit 300 that converts a current signal output from the photodiode 51 into a voltage signal, and an output from the optical receiver circuit 300. The voltage amplifying circuit 15 amplifies a minute voltage signal.

  The anode of the photodiode 51 is connected to the ground electrode GND, and the cathode is connected to the light receiving circuit 300.

  The optical receiving circuit 300 includes an operational amplifier 11 and a feedback resistor 12. The non-inverting input terminal of the operational amplifier 11 is connected to the ground electrode GND. The inverting input terminal of the operational amplifier 11 is connected to the cathode of the photodiode 51. The feedback resistor 12 has one end connected to the output terminal of the operational amplifier 11 and the other end connected to the inverting input terminal of the operational amplifier 11.

  When an optical signal is incident on the photodiode 51, a photocurrent Iin flows through the photodiode 51 from the cathode to the anode. The optical receiving circuit 300 converts the photocurrent Iin output from itself into an output voltage Vo and outputs it.

  When a weak optical signal is received by the optical receiver, the dark current of the photodiode becomes one of noise sources. The dark current is a current unrelated to the optical signal output from the photodiode even when no optical signal is input to the photodiode. In order to improve the reception sensitivity of the optical receiver, it is desirable to reduce the dark current of the photodiode as much as possible. FIG. 2 is a diagram showing the relationship between the bias voltage (anode-cathode voltage) applied to the photodiode and the dark current. A state in which a positive bias voltage is applied is referred to as a forward bias, and a state in which a negative bias voltage is applied is referred to as a reverse bias. In general, the photodiode has the smallest dark current when the bias voltage is 0 (zero).

  In the optical receiver circuit 300 of FIG. 1, it is known that the inverting input terminal and the non-inverting input terminal of the operational amplifier 11 have the same potential due to a phenomenon called imaginary short (virtual short). In other words, the potential of the inverting input terminal of the operational amplifier 11 (= the cathode potential of the photodiode) is the ground potential that is the potential of the non-inverting input terminal. On the other hand, since the anode of the photodiode 51 is grounded, the potential is naturally the ground potential. As described above, the bias voltage of the photodiode 51 of FIG. 1 is 0 (zero), and the photodiode 51 is set to a condition that provides the minimum dark current.

JP 2014-030084 A

  In a general amplifier circuit, there is a voltage region where the output voltage is distorted near the power supply potential and cannot be output correctly. Such a voltage region is called “output headroom” and also occurs in the optical receiver circuit.

  FIG. 3 is a diagram schematically showing output characteristics (current-voltage conversion characteristics) of the optical receiver circuit in consideration of output headroom. The optical receiver circuit is configured as shown in FIG. 1, and is driven by a single positive power supply in which a positive potential VCC is applied to the positive power supply terminal (not shown) of the operational amplifier and a ground potential GND is applied to the negative power supply terminal (not shown). Shall. The output voltage Vo of the optical receiver circuit is expected to operate so as to increase in proportion to the input current Iin (photocurrent output from the photodiode). However, in reality, due to the presence of the output headroom, as shown in FIG. 3, the optical receiving circuit cannot maintain the linearity of the current-voltage conversion characteristics in the vicinity of 0 which is the power supply potential and VCC. Assuming that the voltage of the output headroom is Vhr, the optical receiving circuit can output only the voltage between Vhr and VCC-Vhr as the output voltage Vo.

  For example, in an optical receiver for detecting or measuring a weak optical signal, such as for an optical sensor, the photocurrent output from the photodiode is also very small. Therefore, the optical receiver circuit in the subsequent stage uses a small input current Iin. It must be able to convert voltage accurately. However, as described above, there is an output headroom in the optical receiver circuit, and thus there is a problem that it is difficult for the optical receiver to receive a weak optical signal with high accuracy.

  Accordingly, an object of the present invention is to provide an optical receiver circuit that can accurately receive a weak optical signal regardless of the presence of output headroom in order to solve the above-described problems.

  In order to achieve the above object, the optical receiver circuit according to the present invention connects the photodiode to the operational amplifier in a state where a predetermined constant voltage is applied to both the anode and the cathode of the photodiode.

Specifically, the optical receiver circuit according to the present invention is:
A non-inverting input terminal to which one end of a photodiode is connected, an inverting input terminal to which the other end of the photodiode is connected, and an output that outputs a voltage based on the voltage input to the non-inverting input terminal and the inverting input terminal An operational amplifier having a terminal;
A feedback resistor having one end connected to the output terminal of the operational amplifier and the other end connected to the inverting input terminal of the operational amplifier;
A predetermined constant voltage is applied to the non-inverting input terminal of the operational amplifier.

That is, the optical receiving method according to the present invention is:
A non-inverting input terminal to which one end of a photodiode is connected, an inverting input terminal to which the other end of the photodiode is connected, and an output that outputs a voltage based on the voltage input to the non-inverting input terminal and the inverting input terminal An operational amplifier having a terminal;
A feedback resistor having one end connected to the output terminal of the operational amplifier and the other end connected to the inverting input terminal of the operational amplifier;
An optical receiving method for receiving an optical signal with an optical receiving circuit comprising:
A predetermined constant voltage is applied to the non-inverting input terminal of the operational amplifier.

  As in Patent Document 1, the non-inverting input terminal of the operational amplifier is normally grounded, but a predetermined constant voltage is applied to the optical receiver circuit. By giving this constant voltage, the inverting input terminal becomes the same constant voltage due to an imaginary short. By setting the constant voltage so as to avoid the output headroom, the bias voltage (anode-cathode voltage) of the photodiode is set to 0, and the dark current is minimized, and a weak optical signal can be received with high accuracy. It becomes like this. Therefore, the present invention can provide an optical receiving circuit and an optical receiving method that can accurately receive a weak optical signal regardless of the presence of output headroom.

  In one embodiment of the optical receiver circuit according to the present invention, the one end of the photodiode is an anode and the other end is a cathode, and the predetermined constant voltage is a potential exceeding a negative output headroom voltage of the operational amplifier. It is characterized by that.

  In this optical receiving method, when the photodiode is connected to the operational amplifier with the one end serving as an anode and the other end serving as a cathode, the potential exceeding the negative output headroom voltage of the operational amplifier is set as the predetermined constant voltage. Features.

  In another embodiment of the optical receiver circuit according to the present invention, the one end of the photodiode is a cathode and the other end is an anode, and the predetermined constant voltage is obtained from a positive-side power supply voltage of the operational amplifier from a positive-side output headroom. The potential is smaller than the voltage dropped by the voltage.

  In this optical receiving method, when the photodiode is connected to the operational amplifier with the one end serving as a cathode and the other end serving as an anode, the potential is smaller than a voltage obtained by dropping a positive output headroom voltage from the positive power supply voltage of the operational amplifier. Is the predetermined constant voltage.

  In the optical receiver circuit according to the present invention, the voltage output from the output terminal of the operational amplifier and the predetermined constant voltage are input, and the voltage output from the output terminal of the operational amplifier and the voltage of the predetermined constant voltage. It further comprises a voltage amplifier circuit that amplifies and outputs the difference.

In this optical receiving method, when the output of the output terminal of the operational amplifier is amplified by a voltage amplification circuit having another operational amplifier, the voltage output from the output terminal of the operational amplifier is input to the inverting input terminal of the other operational amplifier. The predetermined constant voltage is input to a non-inverting input terminal of the other operational amplifier, and a voltage difference between the voltage output from the output terminal of the operational amplifier and the predetermined constant voltage is amplified.
By applying the constant voltage as a reference voltage to the voltage amplifier circuit, the offset superimposed on the output voltage of the operational amplifier can be canceled.

  The optical receiver circuit may include a constant voltage source that outputs the predetermined voltage.

  The present invention can provide an optical receiver circuit that can accurately receive a weak optical signal regardless of the presence of output headroom.

It is a figure explaining the optical receiver circuit relevant to this invention. It is a figure explaining the relationship between the bias voltage applied to a photodiode, and dark current. It is a figure explaining the output characteristic of the optical receiver circuit relevant to this invention. It is a figure explaining the optical receiver circuit which concerns on the 1st Embodiment of this invention. It is a figure explaining the circuit of the operational amplifier of the optical receiver circuit concerning the present invention. It is a figure explaining the output characteristic of the optical receiver circuit which concerns on the 1st Embodiment of this invention. It is a figure explaining the optical receiver circuit which concerns on the 3rd Embodiment of this invention. It is a figure explaining the optical receiver circuit which concerns on the 4th Embodiment of this invention. It is a figure explaining the output characteristic of the optical receiver circuit which concerns on the 4th Embodiment of this invention. It is a figure explaining the optical receiver circuit which concerns on the 2nd Embodiment of this invention. It is a figure explaining the optical receiver circuit which concerns on the 3rd Embodiment of this invention. It is a figure explaining the optical receiver circuit which concerns on the 5th Embodiment of this invention. It is a figure explaining the optical receiver circuit which concerns on the 6th Embodiment of this invention. It is a figure explaining the optical receiver circuit which concerns on the 6th Embodiment of this invention.

  Embodiments of the present invention will be described with reference to the accompanying drawings. The embodiments described below are examples of the present invention, and the present invention is not limited to the following embodiments. In the present specification and drawings, the same reference numerals denote the same components.

[First Embodiment]
FIG. 4 is a diagram illustrating the configuration of the optical receiving circuit 301 of the present embodiment.
The optical receiver circuit 301
A non-inverting input terminal to which one end of the photodiode 51 is connected, an inverting input terminal to which the other end of the photodiode 51 is connected, and a voltage based on the voltage input to the non-inverting input terminal and the inverting input terminal are output. An operational amplifier 11 having an output terminal;
A feedback resistor 12 having one end connected to the output terminal of the operational amplifier 11 and the other end connected to the inverting input terminal of the operational amplifier 11;
A constant voltage source 14 for applying a predetermined constant voltage to the non-inverting input terminal of the operational amplifier 11;
Is provided.

  In the present embodiment, the one end of the photodiode 51 is an anode and the other end is a cathode, and the constant voltage source 14 sets a potential exceeding the negative output headroom voltage of the operational amplifier 11 as the predetermined constant voltage.

  The optical receiving circuit 301 according to this embodiment includes an operational amplifier 11, a feedback resistor (R) 12, a phase compensation capacitor (C) 13, and a constant voltage source 14. The non-inverting input terminal (+) of the operational amplifier 11 is connected to the anode of the photodiode (PD) 51 and the constant voltage source 14. The inverting input terminal (−) of the operational amplifier 11 is connected to the cathode of the PD 51. The feedback resistor 12 has one end connected to the output terminal of the operational amplifier 11 and the other end connected to the inverting input terminal of the operational amplifier 11. The phase compensation capacitor 13 has one end connected to the output terminal of the operational amplifier 11 and the other end connected to the inverting input terminal of the operational amplifier 11. The phase compensation capacitor 13 is connected to reduce noise and stabilize negative feedback. A positive potential VCC is applied to the positive power supply terminal of the operational amplifier 11, and a ground potential GND is applied to the negative power supply terminal. The optical receiver circuit 301 functions in the same manner as a current-voltage conversion circuit that converts a current signal output from the PD 51 into a voltage signal.

In the optical receiving circuit 301, the potential of the non-inverting input terminal of the operational amplifier 11 is represented as V1, the potential of the inverting input terminal is represented as V2, and the potential of the output terminal is represented as Vo. A constant voltage Vb is supplied from the constant voltage source 14 to the anode of the PD 51 and the non-inverting input terminal of the operational amplifier 11. Further, the inverting input terminal and the non-inverting input terminal of the operational amplifier 11 have the same potential due to an imaginary short (virtual short). That is,
V1 = V2 = Vb
The relationship holds. Since the inverting input terminal of the operational amplifier 11 and the cathode of the PD 51 are directly connected, both have the same potential. Accordingly, although the anode and cathode potentials of the PD 51 are both Vb, the anode-cathode voltage (referred to as bias voltage) is 0 (zero), and the dark current is minimized.

  FIG. 5 is a diagram illustrating a configuration example of the operational amplifier 11 that configures the optical reception circuit 301. The operational amplifier 11 shown in FIG. 5 includes an input stage, an amplification stage, and an output stage. The differential circuit in the input stage amplifies the potential difference between the two input terminals IN + (non-inverting input terminal) and IN− (inverting input terminal). The next amplification stage increases the gain that is not sufficient with the previous differential circuit alone. The output stage operates as a buffer so as not to be affected by a load such as a resistor connected to the output terminal OUT. When the output stage transistor Q2 is turned on and the source current Isource flows into the output terminal, the output voltage Vo becomes High. On the contrary, when the transistor Q3 in the output stage is turned on and the sink current I sink is extracted from the output terminal, the output voltage Vo becomes Low.

  When the output voltage is high, the potential is a potential dropped from the positive power supply potential VCC by a collector-emitter voltage Vce1 of the transistor Q1, a base-emitter voltage Vbe2 of the transistor Q2, and a voltage drop R1 × Isource due to the resistor R1. It becomes. That is, the maximum output voltage of the output voltage Vo is VCC-Vce1-Vbe2- (R1 × Isource).

  When the output voltage is low, the potential increases from the negative power supply potential GND by the collector-emitter voltage Vce4 of the transistor Q4, the base-emitter voltage Vbe3 of the transistor Q3, and a voltage drop R2 × Isink due to the resistor R2. It becomes. That is, the minimum output voltage of the output voltage Vo is GND + Vce4 + Vbe3 + (R2 × Isink).

  As shown in FIG. 5, in the operational amplifier 11, there is a region where only Vce1 + Vbe2 + (R1 × Isource) is output on the High side and Vce4 + Vbe3 + (R2 × Isink) is not output on the Low side. This is the cause of output headroom. Hereinafter, the output headroom voltage on the High side is expressed as Vhrh, and the output headroom voltage on the Low side is expressed as Vhrl.

  FIG. 6 is a diagram schematically showing output characteristics (current-voltage conversion characteristics) of the optical receiver circuit 301. As described above, the potentials of the non-inverting input terminal and the inverting input terminal of the operational amplifier 11 are both the voltage Vb output from the constant voltage source 14. If the dark current of the PD 51 is ignored, the optical receiver circuit 301 outputs the output voltage Vo = Vb when the photocurrent Iin = 0. As the photocurrent Iin increases, the output voltage Vo increases almost linearly.

  Here, by setting the output voltage Vb of the constant voltage source 14 so as to exceed the low-side output headroom voltage Vhrl, the optical reception circuit 301 can have a small input current Iin as shown in FIG. Voltage conversion can be performed with high accuracy while maintaining linearity.

  As described above, in the optical receiving circuit 301, since the bias voltage (anode-cathode voltage) of the PD 51 becomes 0, the dark current is minimized and the output headroom can be avoided. Therefore, a weak optical signal can be received with high accuracy.

[Second Embodiment]
In the first embodiment, the configuration in which the optical receiving circuit includes the constant voltage source has been described. However, a configuration in which a predetermined constant voltage is applied to the non-inverting input terminal of the operational amplifier from the outside of the optical receiving circuit may be used. FIG. 10 is a diagram for explaining an optical receiver circuit 301a in which a predetermined constant voltage is applied from the outside.

The optical receiving circuit 301a
A non-inverting input terminal to which one end (anode) of PD 51 is connected, an inverting input terminal to which the other end (cathode) of PD 51 is connected, and a voltage based on a voltage input to the non-inverting input terminal and the inverting input terminal. An operational amplifier 11 having an output terminal for output;
A feedback resistor 12 having one end connected to the output terminal of the operational amplifier 11 and the other end connected to the inverting input terminal of the operational amplifier 11;
Is provided.
The optical receiving circuit 301 a may include the phase compensation capacitor 13.
The optical receiving circuit 301a is characterized in that a predetermined constant voltage is applied to the non-inverting input terminal of the operational amplifier from an external constant voltage source.

  The optical receiving circuit 301a does not have a constant voltage source inside, but only a predetermined constant voltage is applied from an external constant voltage source, and the operation is the same as that of the optical receiving circuit 301 in FIG. That is, in the optical receiving circuit 301a, since the bias voltage (anode-cathode voltage) of the PD 51 becomes 0, the dark current is minimized and the output headroom can be avoided. Therefore, a weak optical signal can be received with high accuracy.

[Third Embodiment]
FIG. 7 is a diagram illustrating the optical receiving circuit 302 of the present embodiment. The optical receiver circuit 302 has a configuration in which the voltage amplifier circuit 15 is further connected to the subsequent stage of the operational amplifier 11 with respect to the optical receiver circuit 301 of FIG.

  The voltage amplifier circuit 15 includes an operational amplifier 16. A voltage output from the output terminal of the operational amplifier 11 is input to a non-inverting input terminal of the operational amplifier 16, and the predetermined constant voltage output from the constant voltage source 14 is the output of the operational amplifier 16. The voltage difference between the voltage input to the inverting input terminal and output from the output terminal of the operational amplifier 11 and the predetermined constant voltage output from the constant voltage source 14 is amplified and output. The voltage amplifier circuit 15 further includes at least two resistors (Ra, Rb).

  The non-inverting input terminal (+) of the operational amplifier 16 is connected to the output terminal of the operational amplifier 11. One end of the resistor Ra is connected to the inverting input terminal (−) of the operational amplifier 16, and the other end is connected to the constant voltage source 14. One end of the resistor Rb is connected to the output terminal of the operational amplifier 16, and the other end is connected to the inverting input terminal of the operational amplifier 16.

  With such a configuration, the voltage amplifier circuit 15 operates so as to amplify the difference (Vo−Vb) between the output voltage Vo of the current-voltage converter circuit and the reference voltage Vb by the amplification factor Rb / Ra. As apparent from FIG. 6, the voltage Vb output from the constant voltage source 14 is superimposed on the output voltage Vo of the operational amplifier 11 as an offset. Therefore, the offset superimposed on the output voltage Vo of the operational amplifier 11 can be canceled by applying Vb as a reference voltage to the voltage amplifier circuit 15.

  Even if the voltage amplification circuit 15 is connected to the subsequent stage of the operational amplifier 11 of the optical reception circuit 301a of FIG. 10 as in the optical reception circuit 302a of FIG. 11, the offset superimposed on the output voltage Vo of the operational amplifier 11 is similarly reduced. Can be canceled.

[Fourth Embodiment]
The optical receiver circuit 301 described with reference to FIG. 4 has a configuration in which the anode of the PD 51 is connected to the non-inverting input terminal of the operational amplifier 11 and the cathode of the PD 51 is connected to the inverting input terminal of the operational amplifier 11. On the other hand, even if the polarity of the PD 51 is reversed and connected to the operational amplifier 11, the same effect as the optical receiving circuit 301 can be obtained.

  FIG. 8 is a diagram illustrating the optical receiving circuit 303 of the present embodiment. The optical receiving circuit 303 is connected to the operational amplifier 11 with the polarity of the PD 51 opposite to that of the optical receiving circuit 301 of FIG. In the present embodiment, the one end of the PD 51 is a cathode and the other end is an anode, and the constant voltage source 14 has a potential smaller than a voltage that is dropped from the positive power supply voltage of the operational amplifier 11 by the positive output headroom voltage. Set to a predetermined constant voltage.

  The configuration of the optical receiving circuit 303 is the same as that of the optical receiving circuit 301 in FIG. 4, and a detailed description thereof is omitted. The non-inverting input terminal (+) of the operational amplifier 11 is connected to the cathode of the PD 51 and the constant voltage source 14. The inverting input terminal (−) of the operational amplifier 11 is connected to the anode of the PD 51.

  FIG. 9 is a diagram schematically showing output characteristics (current-voltage conversion characteristics) of the optical receiver circuit 303. The potentials at the non-inverting input terminal and the inverting input terminal of the operational amplifier 11 are both the voltage Vb output from the constant voltage source 14 as in the optical receiver circuit 301 of FIG. If the dark current of the PD 51 is ignored, the optical receiving circuit 303 outputs the output voltage Vo = Vb when the photocurrent Iin = 0. As the photocurrent Iin increases, the output voltage Vo decreases almost linearly. Since the photocurrent Iin flows from the cathode toward the anode, the photocurrent Iin flows into the operational amplifier 11. However, since the optical receiving circuit 303 is an inverting amplifier, the output voltage Vo decreases as the photocurrent Iin increases.

  Here, by setting the output voltage Vb of the constant voltage source 14 to a level lower than the potential (VCC−Vhrh) that is lowered from the positive power supply potential VCC by the High-side output headroom voltage Vhrh, As shown in FIG. 9, even with a very small input current Iin, voltage conversion can be performed with high accuracy while maintaining linearity.

  As described above, in the optical receiving circuit 303, since the bias voltage (anode-cathode voltage) of the PD 51 is 0, the dark current is minimized and the output headroom can be avoided. Therefore, a weak optical signal can be received with high accuracy.

[Fifth Embodiment]
In the fourth embodiment, the configuration in which the optical receiver circuit includes the constant voltage source has been described. However, a predetermined constant voltage may be applied to the non-inverting input terminal of the operational amplifier from the outside of the optical receiver circuit. FIG. 12 is a diagram illustrating an optical receiver circuit 303a in which a predetermined constant voltage is applied from the outside.

  The optical receiving circuit 303a does not have a constant voltage source inside, but only a predetermined constant voltage is applied from an external constant voltage source, and the operation is the same as that of the optical receiving circuit 303 in FIG. That is, in the optical receiving circuit 303a, the bias voltage (anode-cathode voltage) of the PD 51 becomes 0, so that the dark current is minimized and the output headroom can be avoided. Therefore, a weak optical signal can be received with high accuracy.

[Sixth Embodiment]
FIG. 13 is a diagram for explaining the optical receiving circuit 304 of the present embodiment. The optical receiver circuit 304 has a configuration in which a voltage amplifier circuit 15 is further connected downstream of the operational amplifier 11 with respect to the optical receiver circuit 303 of FIG.

  The non-inverting input terminal (+) of the operational amplifier 16 is connected to the output terminal of the operational amplifier 11. One end of the resistor Ra is connected to the inverting input terminal (−) of the operational amplifier 16, and the other end is connected to the constant voltage source 14. One end of the resistor Rb is connected to the output terminal of the operational amplifier 16, and the other end is connected to the inverting input terminal of the operational amplifier 16.

  With such a configuration, the voltage amplifier circuit 15 operates so as to amplify the difference (Vo−Vb) between the output voltage Vo of the current-voltage converter circuit and the reference voltage Vb by the amplification factor Rb / Ra. As apparent from FIG. 9, the voltage Vb output from the constant voltage source 14 is superimposed on the output voltage Vo of the operational amplifier 11 as an offset. Therefore, the offset superimposed on the output voltage Vo of the operational amplifier 11 can be canceled by applying Vb as a reference voltage to the voltage amplifier circuit 15.

  Even if the voltage amplification circuit 15 is connected to the subsequent stage of the operational amplifier 11 of the optical reception circuit 303a of FIG. 12 as in the optical reception circuit 304a of FIG. 14, the offset superimposed on the output voltage Vo of the operational amplifier 11 is similarly reduced. Can be canceled.

[Effect of the invention]
The optical receiving circuit according to the present invention receives a weak optical signal with high accuracy by connecting the PD 51 to the current-voltage conversion circuit in a state where a predetermined constant voltage is applied to both the anode and the cathode of the PD 51. Will be able to.

11: operational amplifier 12: feedback resistor 13: phase compensation capacitor 14: constant voltage source 15: voltage amplifier circuit 16: operational amplifier 51: photodiode 300, 301, 301a, 302, 302a, 303, 303a, 304, 304a: optical receiver circuit

Claims (4)

A non-inverting input terminal to which one end of a photodiode is connected, an inverting input terminal to which the other end of the photodiode is connected, and an output that outputs a voltage based on the voltage input to the non-inverting input terminal and the inverting input terminal An operational amplifier having a terminal;
A feedback resistor having one end connected to the output terminal of the operational amplifier and the other end connected to the inverting input terminal of the operational amplifier;
A predetermined constant voltage is applied to the non-inverting input terminal of the operational amplifier .
The one end of the photodiode is an anode and the other end is a cathode;
The optical receiver circuit according to claim 1, wherein the predetermined constant voltage is a potential that exceeds a negative output headroom voltage of the operational amplifier . A non-inverting input terminal to which one end of a photodiode is connected, an inverting input terminal to which the other end of the photodiode is connected, and an output that outputs a voltage based on the voltage input to the non-inverting input terminal and the inverting input terminal An operational amplifier having a terminal;
A feedback resistor having one end connected to the output terminal of the operational amplifier and the other end connected to the inverting input terminal of the operational amplifier;
A predetermined constant voltage is applied to the non-inverting input terminal of the operational amplifier .
The one end of the photodiode is a cathode and the other end is an anode;
The predetermined constant voltage is set to a potential smaller than a voltage obtained by dropping a positive output headroom voltage from a positive power supply voltage of the operational amplifier.
An optical receiver circuit . Voltage amplification that outputs a voltage output from the output terminal of the operational amplifier and the predetermined constant voltage, and amplifies a voltage difference between the voltage output from the output terminal of the operational amplifier and the predetermined constant voltage. optical receiving circuit according to claim 1 or 2, further comprising a circuit. The optical receiver circuit according to any one of claims 1 to 3 , wherein the optical receiver circuit includes a constant voltage source that outputs the predetermined voltage.

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