JP2021061456A - Optical receiving circuit - Google Patents

Abstract

To provide an optical receiving circuit capable of generating a signal corresponding to reflected light from an object even immediately after receiving high-intensity light.SOLUTION: An optical receiving unit 14 includes an operational amplifier U1 that receives a current output from a receiving element APD at an inverting input terminal and outputs a light receiving signal RS having a signal level corresponding to the current received at the inverting input terminal from the output terminal, and a switching element composed of a Schottky barrier diode D that is electrically connected between the inverting input terminal and the output terminal of the operational amplifier, and transmits a current from the inverting input terminal to the output terminal when the potential of the inverting input terminal is higher than the potential of the output terminal by a predetermined potential or more, and stops the transmission of the current when the potential of the inverting input terminal is lower than the potential higher than the potential of the output terminal by the predetermined potential.SELECTED DRAWING: Figure 2

Description

The present invention relates to an optical receiving circuit that converts received light into an electric signal.

A ranging device that measures the distance to an object by irradiating the object with a laser beam and receiving and analyzing the laser beam reflected by the object is known (see, for example, Patent Document 1). ). In such a ranging device, for example, a pulsed laser beam whose light intensity is modulated by a sine wave is irradiated to an object, the laser beam reflected by the object is received, and the light intensity is converted into an electric signal. Then, the phase difference between the sine wave component contained in the electric signal and the sine wave component contained in the light intensity of the laser beam at the time of emission is extracted, and the extracted phase difference is converted into a delay time, and the delay time and the delay time are obtained. Calculate the distance to the object based on the speed of light.

Here, as an optical receiving circuit that converts the light intensity of the received laser light into an electric signal, a circuit including a photodiode and a transimpedance amplifier has been proposed (see, for example, Patent Document 2). In a transimpedance amplifier (hereinafter referred to as TIA), an input terminal and an output terminal are connected to each other by a feedback resistor, and the current output from the photodiode is received by the input terminal. With such a configuration, the TIA converts the current output from the photodiode into a voltage and outputs this from the output terminal.

By the way, the above-mentioned TIA is set to have a relatively high gain in order to detect the weak light reflected by a distant object.

Therefore, when relatively high-intensity light from a nearby object enters the photodiode, the TIA may become saturated. At this time, the photodiode supplies the TIA with a large current exceeding the limit of the linear operation of the TIA, and brings the TIA to a saturated state. When the TIA is saturated, the TIA outputs an electric signal having a wide pulse width.

Therefore, in order to avoid such a saturation state, a clip circuit made of a diode is connected to the input terminal of the TIA. The diode has its anode connected to the input terminal of the TIA. Further, a saturation threshold value, which is a voltage value at the boundary of whether the TIA operates in the unsaturated state or the saturated state, is applied to the cathode of the diode.

With this configuration, when a voltage higher than the saturation threshold is applied to the input terminal of the TIA, the clip circuit (diode) forcibly clips the voltage value of the input terminal to a voltage value lower than the saturation threshold. This avoids the saturation state.

JP-A-2015-129646 JP-A-2018-163156

By the way, the voltage value of the input terminal of the TIA depends not only on the current output from the photodiode but also on the output voltage of the TIA via the feedback resistor. That is, the clip circuit (diode) starts the above operation after a voltage exceeding the saturation threshold is applied to the input terminal of the TIA. Therefore, the TIA operates by temporarily receiving a voltage exceeding the saturation threshold value, and as a result, becomes saturated and outputs an electric signal having a wide pulse width over a certain amount.

As a result, the pulse in the electric signal corresponding to the reflected light from the object to be measured is originally masked by the wide pulse in the electric signal corresponding to the high-intensity reflected light described above, and the distance is increased. Measurement becomes impossible.

Therefore, even with the configuration described in Patent Document 2, the TIA is temporarily saturated immediately after receiving high-intensity light, so that an electric signal including a pulse corresponding to the reflected light from the object to be measured is included. One example of the problem is that it becomes difficult to generate.

Therefore, one of the objects of the present invention is to provide an optical receiving circuit capable of generating a signal corresponding to the reflected light from an object even immediately after receiving high-intensity light.

The invention according to claim 1 corresponds to a light receiving element that outputs a current corresponding to the intensity of the received light, and the current received from the light receiving element at the input terminal and corresponding to the current received at the input terminal. When the electric current that outputs a light receiving signal having a signal level from the output terminal is electrically connected between the input terminal and the output terminal, and the potential of the input terminal is higher than the potential of the output terminal by a predetermined potential or more. While the current is sent from the input terminal to the output terminal, the current transmission is stopped when the potential of the input terminal is lower than the potential of the output terminal by the predetermined potential. It is characterized by having a switch element.

The invention according to claim 8 corresponds to a light receiving element that outputs a current corresponding to the intensity of the received light, and the current received from the light receiving element at the input terminal and corresponding to the current received at the input terminal. It is characterized by including an operational amplifier that outputs a light receiving signal having a signal level from an output terminal, and a diode in which an anode is connected to the input terminal and a cathode is connected to the output terminal.

It is a figure which represents typically the ranging device 100 including the optical receiving circuit which concerns on this invention. It is a circuit diagram which shows an example of the optical receiving circuit included in the optical receiving part 14. It is an equivalent circuit diagram of the light receiving circuit when receiving low intensity light. It is an equivalent circuit diagram of the light receiving circuit when receiving high intensity light. It is a figure which shows the pulse waveform of the light-receiving signal RS when the operational amplifier U1 is in a non-saturated state, and the pulse waveform of a light-receiving signal RS when it is in a saturated state, in comparison. It is a circuit diagram which shows the structure of the current-voltage conversion circuit 14Ba as a modification of the current-voltage conversion circuit 14B. It is a circuit diagram which shows another example of the optical receiving circuit included in the optical receiving part 14.

Hereinafter, preferred embodiments of the present invention will be described in detail.

FIG. 1 is a diagram schematically showing a distance measuring device 100 including an optical receiving circuit according to the present invention. The distance measuring device 100 scans a predetermined area (hereinafter referred to as a scanning area) with a pulsed laser beam, and measures a distance to an object existing in the scanning area. It is a device.

The distance measuring device 100 includes a light source 11, a rotating element 12, a separating element 13, an optical receiving unit 14, and a control unit 15.

The light source 11 intermittently emits laser light having a peak wavelength in the infrared region, for example. As a result, the light source 11 irradiates the separation element 13 with pulsed laser light (hereinafter referred to as pulsed light) as emitted light L1.

The separation element 13 is, for example, a beam splitter, which reflects the emitted light L1 emitted from the light source 11 and guides it to the rotating element 12, while transmitting the reflected light reflected by the rotating element 12 and passing the light. It leads to the receiving unit 14.

The rotating element 12 is, for example, a MEMS (Micro Electro Mechanical System) mirror as a so-called rotating mirror having one light reflecting surface 12S that periodically rotates on a rotating shaft AX and AY orthogonal to each other. The light reflecting surface 12S reflects the emitted light L1 received through the separating element 13, and emits the reflected light as scanning light L2. That is, the rotating element 12 uses a virtual plane separated from itself by a predetermined distance as a scanning surface R1 (a region surrounded by a single point chain line in FIG. 1), faces the scanning surface R1, and the scanning surface R1. The pulsed light based on the pulsed reflected light L1 is emitted as the scanning light L2 so as to scan the inside.

Here, when the scanning light L2 hits an object OB (an object or substance having reflexivity or scattering property with respect to the scanning light L2) as shown in FIG. 1, the scanning light L2 is reflected or reflected by the object OB. Scattered. The pulsed light reflected by the object OB in this way travels in the same optical path as the scanning light L2 as the reflected light L3 in the direction opposite to the scanning light L2, and is irradiated to the rotating element 12. To. Therefore, at this time, the rotating element 12 reflects the reflected light L3 as pulsed light on its own light reflecting surface 12S, and guides this to the light receiving unit 14 via the separating element 13.

The light receiving unit 14 receives, for example, the reflected light L3, generates a light receiving signal RS having a signal level corresponding to the light intensity of the reflected light L3, and supplies the light receiving signal RS to the control unit 15.

The control unit 15 includes a light source control unit 15A that drives and controls the light source 11 described above, and a rotating element control unit 15B that drives and controls the rotating element 12.

Further, the control unit 15 has a distance measuring unit 15C that measures the distance to the object OB as shown in FIG. 1 based on the light receiving signal RS supplied from the light receiving unit 14.

For example, the ranging unit 15C first detects a pulse waveform corresponding to the pulsed reflected light L3 from the received signal RS, and receives the reflected light L3 at the time point of the rising or falling edge of the pulse waveform. Get as timing. Then, the distance measuring unit 15C obtains the distance from the distance measuring device 100 to the object OB based on the time difference between the light receiving timing of the reflected light L3 and the emitting timing of the scanning light L2, and the measurement distance data representing the distance is obtained. Output LD.

In the distance measuring device 100, the light receiving unit 14 described above is an optical receiving circuit capable of avoiding saturation of the operational amplifier included in the light receiving unit 14 when receiving high-intensity light (including reflected light L3). Is adopted.

FIG. 2 is a circuit diagram showing an example of an optical receiving circuit included in the optical receiving unit 14.

As shown in FIG. 2, the optical receiving circuit includes a photoelectric conversion circuit 14A and a current-voltage conversion circuit 14B.

The photoelectric conversion circuit 14A includes a light receiving element APD that outputs a current corresponding to the light intensity of the reflected light L3 when irradiated with light, for example, the reflected light L3. As the light receiving element APD, it is assumed that the light intensity of the reflected light from a general object excluding an object having a high light reflectance surface such as a road sign or a curved mirror is weak. , Use an avalanche photodiode with high light detection sensitivity.

A predetermined power supply potential Vh is applied to the cathode terminal of the light receiving element APD. For example, when the light receiving element APD receives the reflected light L3, a current corresponding to the light intensity of the reflected light L3 is output from the anode terminal, and this is converted into current and voltage. It is sent to the circuit 14B.

The current-voltage conversion circuit 14B includes an operational amplifier U1, a resistor Rf, and a diode D.

The operational amplifier U1 receives the current output from the light receiving element APD described above at the inverting input terminal. A predetermined reference potential Vref is applied to the non-inverting input terminal of the operational amplifier U1.

A resistor Rf as a feedback resistor and a diode D are electrically connected in parallel between the inverting input terminal and the output terminal of the operational amplifier U1. That is, one end of the resistor Rf is electrically connected to the inverting input terminal of the operational amplifier U1, and the other end of the resistor Rf is electrically connected to the output terminal of the operational amplifier U1. Further, the anode terminal of the diode D is electrically connected to the inverting input terminal of the operational amplifier U1, and the cathode terminal of the diode D is electrically connected to the output terminal of the operational amplifier U1.

With the above configuration, the current-voltage conversion circuit 14B sets the current output from the light receiving element APD, that is, the current having a magnitude corresponding to the intensity of the light received by the light receiving element APD, to the voltage having a magnitude corresponding to this current. Convert to. The voltage value of the converted voltage depends on the gain of the operational amplifier U1 set based on the resistance value of the resistor Rf, which is a feedback resistor. Then, the current-voltage conversion circuit 14B outputs a signal having a level corresponding to the voltage as the above-mentioned received light signal RS.

Here, in the current-voltage conversion circuit 14B shown in FIG. 2, when the light receiving element APD receives low-intensity light, for example, the reflected light L3 from a general object as described above, the light receiving element APD outputs the light. The current produced is small. Therefore, the voltage between the inverting input terminal and the output terminal of the operational amplifier U1 becomes equal to or lower than the forward voltage of the diode D due to the current, and therefore the diode D is turned off. At this time, the diode D becomes a capacitor having a capacitance between its own terminals equivalently.

FIG. 3A is an equivalent circuit diagram of an optical receiving circuit (14A, 14B) when the light receiving element APD receives low-intensity light. That is, when receiving low-intensity light, the diode D is in a state of being represented as a capacitor Cd having a capacitance between its own terminals.

Therefore, for example, when the light receiving element APD receives the low-intensity pulsed reflected light L3, the current-voltage conversion circuit 14B has a signal level corresponding to the light intensity of the reflected light L3 and has a pulse of the reflected light L3. A light receiving signal RS including a pulse having a pulse width equal to the width is output.

On the other hand, high-intensity stray light generated by scattering or reflection of emitted light L1 in an optical system including a light source 11, a rotating element 12, a separation element 13, and an optical receiving unit 14, and high-intensity reflection from an object to be measured. When the light receiving element APD receives light, the diode D is turned on. Specifically, when the voltage between the inverting input terminal and the output terminal of the operational amplifier U1 becomes equal to or higher than the forward voltage of the diode D because the large current output by the light receiving element APD is received in response to high-intensity light. , The diode D is turned on. At this time, the diode D becomes a resistor equivalently represented by its own resistance component.

FIG. 3B is an equivalent circuit diagram of an optical receiving circuit (14A, 14B) when the light receiving element APD receives high-intensity light. That is, when receiving high-intensity light, the diode D is in a state of being represented as a resistor Rd having a resistance value corresponding to its own resistance component. At this time, the combined resistance due to the resistor Rd and the resistor Rf as the feedback resistor becomes extremely low, and the operational amplifier U1 is in a state close to full feedback. Therefore, as the operational amplifier U1, an operational amplifier that guarantees stable operation with a gain of “1” or more and oscillation does not occur is used.

When the diode D is turned on as described above, a current is sent from the inverting input terminal of the operational amplifier U1 toward the output terminal, and the voltage of the output terminal of the operational amplifier U1 is clipped to the forward voltage of the diode D. ..

As a result, the voltage of the output terminal of the operational amplifier U1 is clipped to the forward voltage when the inverting input terminal of the operational amplifier U1 receives an excessive input enough to bring the operational amplifier U1 to a saturated state. That is, immediately before the operational amplifier U1 performs the operation corresponding to the excessive input, the state in which the operational amplifier U1 is saturated is avoided, and the non-saturated state is maintained.

By the way, when the operational amplifier U1 is saturated, the pulse width of the pulse included in the light receiving signal RS output from the operational amplifier U1 is compared with the pulse width of the pulsed light (including the reflected light L3) received by the light receiving element APD. Spreads significantly.

FIG. 4 is a diagram showing a comparison between the pulse waveform of the light receiving signal RS when the operational amplifier U1 is in the non-saturated state and the pulse waveform of the light receiving signal RS when the operational amplifier U1 is in the saturated state.

As shown in FIG. 4, when the operational amplifier U1 is in the unsaturated state, a pulse P1 having a pulse width W1 equal to the pulse width of the pulsed light received by the light receiving element APD appears in the light receiving signal RS.

On the other hand, when the operational amplifier U1 is saturated, a pulse P2 having a pulse width W2 wider than the pulse width W1 of the pulsed light received by the light receiving element APD appears in the light receiving signal RS. Therefore, even if the light receiving element APD receives the reflected light L3 from the object OB as shown in FIG. 1 during this period, the pulse corresponding to the reflected light L3 is masked by the pulse P2 shown in FIG. Therefore, it is impossible to measure the distance to the object OB.

However, as described above, in the current-voltage conversion circuit 14B, even when the operational amplifier U1 receives an excessive input because the light receiving element APD receives high-intensity pulsed light due to stray light or the like, the clipping operation by the diode D causes the said. Saturation of operational amplifier U1 is avoided. As a result, the operational amplifier U1 outputs a light receiving signal RS including a pulse P1 having a pulse width W1 shown by a thick solid line in FIG. 4, for example, corresponding to the high-intensity stray light (pulse light) received by the light receiving element APD. ..

Therefore, according to the current-voltage conversion circuit 14B, it is possible to generate a light-receiving signal RS including a pulse corresponding to the reflected light from the object to be measured even immediately after the light-receiving element APD receives high-intensity light. It becomes.

Here, it is conceivable to use a pn junction diode, a Schottky barrier diode, or the like as the diode D, but it is desirable to use a Schottky barrier diode for the following reasons.

That is, in the case of a pn junction diode, even if the state is switched from the forward bias state (FIG. 3A) to the reverse bias state (FIG. 3B), a relatively large reverse current flows immediately after the switching due to the minority carrier accumulation effect. Therefore, when a pn junction diode is used as the diode D, the reverse current of the diode D is converted into a voltage via the resistor Rf when recovering from the excessive input, and the width of the pulse in the received signal RS is widened by that voltage. It ends up.

On the other hand, in the Schottky barrier diode, since the current flowing in the forward direction has a large number of carriers, the effect of accumulating a small number of carriers hardly occurs. Therefore, when the Schottky barrier diode is adopted as the diode D, the width of the pulse in the received light signal RS at the time of excessive input can be narrowed as compared with the case where the pn junction diode is adopted.

By the way, except at the time of the above-mentioned excessive input, the diode D of the current-voltage conversion circuit 14B is turned off, and as shown in FIG. 3A, it behaves as a capacitor Cd equivalently. Therefore, this capacitor Cd may also serve as phase compensation for the operational amplifier U1. However, when the input is excessive, the capacitor Cd disappears as shown in FIG. 3B. Therefore, when the state is restored to the state shown in FIG. 3A, an undershoot may occur at the edge portion of the pulse included in the received light signal RS. Therefore, if it is not desired to cause such an undershoot, a capacitor for phase compensation may be separately provided in parallel with the resistor Rf as a feedback resistor.

Further, in the example shown in FIG. 2, as the current-voltage conversion circuit 14B, a single diode D electrically connected between the inverting input terminal and the output terminal of the operational amplifier U1 is adopted. However, a plurality of diodes D may be electrically connected between the inverting input terminal and the output terminal of the operational amplifier U1.

FIG. 5 is a circuit diagram showing a configuration of a current-voltage conversion circuit 14Ba as a modification of the current-voltage conversion circuit 14B, which was made in view of this point. In the configuration shown in FIG. 5, the diodes D1 to Dn (n is an integer of 2 or more) connected in series in the forward direction are used instead of the diode D, and other configurations (14A, Rf, U1) are used. ) Is the same as that shown in FIG. In the example shown in FIG. 5, the anode of D1 of the diodes D1 to Dn is electrically connected to the inverting input terminal of the operational amplifier U1, and the cathode of the diode Dn is electrically connected to the output terminal of the operational amplifier U1. There is. Further, in the row of diodes D1 to Dn, the cathode of the k (k is an integer of 1 to n-1) th diode Dk is connected to the anode of the (k + 1) th diode D (k + 1).

Here, when the forward voltage of each of the diodes D1 to Dn is Vf, the voltage for clipping the operational amplifier U1 at the time of the excessive input as described above is nVf. Therefore, by determining the number n of the diodes D in consideration of the noise and dynamic range of the circuit element (for example, AD converter) in the subsequent stage that receives the light receiving signal RS output from the optical receiving unit 14, the number n of the diodes D is determined at the time of excessive input. It is possible to set an appropriate maximum level of the received signal RS.

FIG. 6 is a circuit diagram showing another example of the optical receiving circuit included in the optical receiving unit 14.

In the optical receiving unit 14 shown in FIG. 6, a photoelectric conversion circuit 14Ac is adopted instead of the photoelectric conversion circuit 14A, and a current-voltage conversion circuit 14Bc is adopted instead of the current-voltage conversion circuit 14B. In FIG. 6, the light receiving element APD, the operational amplifier U1, and the resistor Rf are the same as those shown in FIG.

In the photoelectric conversion circuit 14Ac shown in FIG. 6, the light receiving element APD receives the power supply potential Vh at the cathode terminal via the resistor Rlim. Further, the other end of the capacitor Cph whose one end is grounded is connected to the cathode terminal of the light receiving element APD.

In the current-voltage conversion circuit 14Bc shown in FIG. 6, the operational amplifier U1 operates by receiving the power supply potential Vcc at the power supply terminal. The power supply terminal of the operational amplifier U1 is connected to the other end of the capacitor Cp1 to which the ground potential is applied to one end thereof.

A voltage dividing potential obtained by dividing the power supply potential Vcc by the resistors Rb1 and Rb2 is applied as a reference potential Vref to the non-inverting input terminal of the operational amplifier U1. Further, the other end of the capacitor Cp2 whose one end is grounded is connected to the non-inverting input terminal.

A resistor Rf and a phase compensation capacitor Cf, which are connected in parallel to each other, are connected between the inverting input terminal and the output terminal of the operational amplifier U1. Further, diodes D1 and D2 connected in series with each other are connected between the inverting input terminal and the output terminal of the operational amplifier U1. At this time, the anode terminal of the diode D1 is electrically connected to the inverting input terminal of the operational amplifier U1, and the cathode terminal of the diode D1 is connected to the anode terminal of the diode D2. The cathode terminal of the diode D2 is electrically connected to the output terminal of the operational amplifier U1. Also in the configuration shown in FIG. 6, Schottky barrier diodes are used as the diodes D1 and D2.

In the above embodiment, an avalanche photodiode is used as the light receiving element APD, but a pn junction type photodiode may be used when high sensitivity is not required. Further, instead of the above-mentioned light receiving element APD, a light receiving element such as a photoresistor, a phototransistor, a CCD (Charge-Coupled Device), or a photomultiplier tube may be used. That is, the light receiving element used in the light receiving unit 14 may be any one that outputs a current corresponding to the intensity of the received light.

Further, in the above embodiment, in order to avoid the saturated state when the operational amplifier U1 receives an excessive input that saturates, a diode D composed of a Schottky barrier diode is used as a switching element for the inverting input terminal and the output of the operational amplifier U1. It is electrically connected between the terminals. However, a pn junction diode or a transistor may be used as the switching element.

In short, in order to avoid saturation of the operational amplifier U1 at the time of excessive input, a switching element that performs the following operations may be electrically connected between the inverting input terminal and the output terminal of the operational amplifier U1. That is, when the potential of the inverting input terminal of the operational amplifier U1 is higher than the potential of the output terminal (corresponding to the forward voltage of the switching element itself) or more, the switching element is directed from the input terminal to the output terminal. Sends an electric current. On the other hand, when the potential of the inverting input terminal of the operational amplifier U1 is lower than the potential higher than the potential of the output terminal by a predetermined potential, the switching element stops the transmission of the current as described above.

14A Photoelectric conversion circuit 14B Current-voltage conversion circuit 100 Distance measuring device APD Light receiving element D, D1 to Dn Diode Rf Resistance U1 Operational amplifier

Claims (14)

A light receiving element that outputs a current corresponding to the intensity of the received light, and
An operational amplifier that receives the current output from the light receiving element at the input terminal and outputs a light receiving signal having a signal level corresponding to the current received at the input terminal from the output terminal.
When the input terminal and the output terminal are electrically connected and the potential of the input terminal is higher than the potential of the output terminal by a predetermined potential or more, a current is sent from the input terminal to the output terminal. On the other hand, the optical receiving circuit is characterized by having a switch element for stopping the transmission of a current when the potential of the input terminal is lower than the potential of the output terminal by the predetermined potential. The optical receiving circuit according to claim 1, wherein one end is electrically connected to the input terminal and the other end includes a resistor electrically connected to the output terminal. The switch element according to claim 1 or 2, wherein the switch element is a Schottky barrier diode in which the anode is electrically connected to the input terminal and the cathode is electrically connected to the output terminal. Optical receiving circuit. The switch element is composed of the first to nth Schottky barrier diodes connected in series in the forward direction, and the first of the first to nth (n is an integer of 2 or more) Schottky barrier diodes. The first or second aspect of claim 1 or 2, wherein the anode of the Schottky barrier diode of 1 is connected to the input terminal, and the cathode of the nth Schottky barrier diode is connected to the output terminal. Optical receiving circuit. The optical receiving circuit according to any one of claims 1 to 4, wherein the light receiving element is an avalanche photodiode whose anode is electrically connected to the input terminal. The optical receiving circuit according to any one of claims 1 to 5, wherein one end is connected to the input terminal and the other end includes a capacitor connected to the output terminal. The input terminal is an inverting input terminal of the operational amplifier.
The optical receiving circuit according to any one of claims 1 to 6, wherein a predetermined reference potential is applied to the non-inverting input terminal of the operational amplifier. A light receiving element that outputs a current corresponding to the intensity of the received light, and
An operational amplifier that receives the current output from the light receiving element at the input terminal and outputs a light receiving signal having a signal level corresponding to the current received at the input terminal from the output terminal.
An optical receiving circuit comprising a diode having an anode connected to the input terminal and a cathode connected to the output terminal. The optical receiving circuit according to claim 8, wherein one end is electrically connected to the input terminal and the other end includes a resistor electrically connected to the output terminal. The optical receiving circuit according to claim 8 or 9, wherein the diode is a Schottky barrier diode. The diode is composed of the first to nth Schottky barrier diodes connected in series in the forward direction, and the first of the first to nth (n is an integer of 2 or more) Schottky barrier diodes. The light according to claim 8 or 9, wherein the anode of the Schottky barrier diode of the above is connected to the input terminal, and the cathode of the nth Schottky barrier diode is connected to the output terminal. Receiver circuit. The optical receiving circuit according to any one of claims 8 to 11, wherein the light receiving element is an avalanche photodiode whose anode is electrically connected to the input terminal. The optical receiving circuit according to any one of claims 8 to 12, wherein one end is connected to the input terminal and the other end includes a capacitor connected to the output terminal. The input terminal is an inverting input terminal of the operational amplifier.
The optical receiving circuit according to any one of claims 8 to 13, wherein a predetermined reference potential is applied to the non-inverting input terminal of the operational amplifier.

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